libbpf-tools/klockstat: accept lock addr as well as lock name

The following PR added printing for lock addr and name in max acq/hold times:

* iovisor#4188

This is how it looks like:

```
$ sudo ./klockstat -d 5 -c down_ -n 2 -s 2 -S hld_total -p 39643
Tracing mutex/sem lock events...  Hit Ctrl-C to end

                               Caller  Avg Wait    Count   Max Wait   Total Wait
                        down_read+0x5    8.0 us    10685    83.2 ms      85.0 ms
           kernfs_iop_permission+0x27
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)

                               Caller  Avg Wait    Count   Max Wait   Total Wait
                        down_read+0x5    2.1 us    36025    71.1 ms      76.8 ms
           kernfs_iop_permission+0x27
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)

                               Caller  Avg Hold    Count   Max Hold   Total Hold
               down_read_killable+0x5    8.2 us    19386   297.7 us     158.1 ms
                     iterate_dir+0x52
                              Max PID 39643, COMM cadvisor, Lock no-ksym (0xffff9477eec5f1a8)

                               Caller  Avg Hold    Count   Max Hold   Total Hold
                        down_read+0x5    209 ns    82630     8.9 us      17.3 ms
             kernfs_fop_readdir+0x115
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)
```

Previously it was possible to filter on lock name only:

```
$ sudo ./klockstat -d 5 -c down_ -n 2 -s 2 -S hld_total -p 39643 -L kernfs_rwsem
Tracing mutex/sem lock events...  Hit Ctrl-C to end

                               Caller  Avg Wait    Count   Max Wait   Total Wait
                        down_read+0x5    1.5 us    32126    41.3 ms      46.9 ms
           kernfs_iop_permission+0x27
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)

                               Caller  Avg Wait    Count   Max Wait   Total Wait
                        down_read+0x5    156 ns    66104    94.6 us      10.3 ms
             kernfs_fop_readdir+0x115
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)

                               Caller  Avg Hold    Count   Max Hold   Total Hold
                        down_read+0x5    305 ns    66104    97.8 us      20.2 ms
             kernfs_fop_readdir+0x115
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)

                               Caller  Avg Hold    Count   Max Hold   Total Hold
                        down_read+0x5    115 ns    32126     5.5 us       3.7 ms
           kernfs_iop_permission+0x27
                              Max PID 39643, COMM cadvisor, Lock kernfs_rwsem (0xffffffff89f87e00)
Exiting trace of mutex/sem locks
```

Now it's also possible to filter on lock addr:

```
$ sudo ./klockstat -d 5 -c down_ -n 2 -s 2 -S hld_total -p 39643 -L 0xffff9477eec5f1a8
Tracing mutex/sem lock events...  Hit Ctrl-C to end

                               Caller  Avg Wait    Count   Max Wait   Total Wait
               down_read_killable+0x5    227 ns       68     1.0 us      15.4 us
                     iterate_dir+0x52
                              Max PID 39643, COMM cadvisor, Lock no-ksym (0xffff9477eec5f1a8)

                               Caller  Avg Hold    Count   Max Hold   Total Hold
               down_read_killable+0x5  191.5 us       68   238.3 us      13.0 ms
                     iterate_dir+0x52
                              Max PID 39643, COMM cadvisor, Lock no-ksym (0xffff9477eec5f1a8)
```

This is useful for locks that are per process, like `mmap_lock`.

libbpf-tools/klockstat.c

@@ -83,7 +83,7 @@ static const char program_doc[] =
 " klockstat -t 181 # trace thread 181 only\n"
 " klockstat -c pipe_ # print only for lock callers with 'pipe_'\n"
 " # prefix\n"
-" klockstat -L cgroup_mutex # trace the cgroup_mutex lock only\n"
+" klockstat -L cgroup_mutex # trace the cgroup_mutex lock only (accepts addr too)\n"
 " klockstat -S acq_count # sort lock acquired results by acquire count\n"
 " klockstat -S hld_total # sort lock held results by total held time\n"
 " klockstat -S acq_count,hld_total # combination of above\n"
@@ -114,11 +114,17 @@ static const struct argp_option opts[] = {
  {},
 };
 
+static void *parse_lock_addr(const char *lock_name) {
+ unsigned long lock_addr;
+
+ return sscanf(lock_name, "0x%lx", &lock_addr) ? (void*)lock_addr : NULL;
+}
+
 static void *get_lock_addr(struct ksyms *ksyms, const char *lock_name)
 {
  const struct ksym *ksym = ksyms__get_symbol(ksyms, lock_name);
 
- return ksym ? (void*)ksym->addr : NULL;
+ return ksym ? (void*)ksym->addr : parse_lock_addr(lock_name);
 }
 
 const char *get_lock_name(struct ksyms *ksyms, unsigned long addr)