Fix for verifier failure in wakeuptime

On my system, the manually unrolled stack walker fails the verifier, due
to what seems to me like an incorrect return statement. Setting bp = 0
has no effect, seems that the intent was to return 0 instead.

Not sure why others haven't hit this, but the fix contained here seems
reasonable.

Signed-off-by: Brenden Blanco <[email protected]>

tools/wakeuptime.py

@@ -81,7 +81,7 @@ def signal_ignore(signal, frame):
  if (bpf_probe_read(&ret, sizeof(ret), (void *)(*bp+8)))
  return 0;
  if (bpf_probe_read(bp, sizeof(*bp), (void *)*bp))
- bp = 0;
+ return 0;
  if (ret < __START_KERNEL_map)
  return 0;
  return ret;