kprobes: Use bool type for functions which returns boolean value

Use the 'bool' type instead of 'int' for the functions which
returns a boolean value, because this makes clear that those
functions don't return any error code.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v2:
  - Fix trace_kprobe's kprobe_gone() too.
3 files changed