ksnoop: Fix info command output

The info command is used to print kernel function signature.
This commit makes the output conform to the kernel code style.
Before this fix:
```
$ sudo ./ksnoop info sk_alloc
struct sock  *  sk_alloc(struct net  * net, int family, gfp_t priority, struct proto  * prot, int kern);
$ sudo ./ksnoop info dma_buf_end_cpu_access
$ sudo ./ksnoop info array_map_alloc_check
int array_map_alloc_check(unionbpf_attr *attr);
```
After this fix:
```
$ sudo ./ksnoop info sk_alloc
struct sock *sk_alloc(struct net *net, int family, gfp_t priority, struct proto *prot, int kern);
$ sudo ./ksnoop info dma_buf_end_cpu_access
int dma_buf_end_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction);
$ sudo ./ksnoop info array_map_alloc_check
int array_map_alloc_check(union bpf_attr *attr);
```

Signed-off-by: Hengqi Chen <[email protected]>

libbpf-tools/ksnoop.c

@@ -419,11 +419,12 @@ static char *type_id_to_str(struct btf *btf, __s32 type_id, char *str)
  name = btf__str_by_offset(btf, type->name_off);
  break;
  case BTF_KIND_UNION:
- prefix = "union";
+ prefix = "union ";
  name = btf__str_by_offset(btf, type->name_off);
  break;
  case BTF_KIND_ENUM:
  prefix = "enum ";
+ name = btf__str_by_offset(btf, type->name_off);
  break;
  case BTF_KIND_TYPEDEF:
  name = btf__str_by_offset(btf, type->name_off);
@@ -445,7 +446,7 @@ static char *value_to_str(struct btf *btf, struct value *val, char *str)
 
  str = type_id_to_str(btf, val->type_id, str);
  if (val->flags & KSNOOP_F_PTR)
- strncat(str, " * ", MAX_STR);
+ strncat(str, "*", MAX_STR);
  if (strlen(val->name) > 0 &&
  strcmp(val->name, KSNOOP_RETURN_NAME) != 0)
  strncat(str, val->name, MAX_STR);
@@ -680,7 +681,7 @@ static int cmd_info(int argc, char **argv)
  for (i = 0; i < nr_traces; i++) {
  struct func *func = &traces[i].func;
 
- printf("%s %s(",
+ printf("%s%s(",
  value_to_str(traces[i].btf, &func->args[KSNOOP_RETURN],
  str),
  func->name);