signal: make sigkill_pending() return bool

sigkill_pending() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-17-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -1904,10 +1904,10 @@ static inline bool may_ptrace_stop(void)
  * Return non-zero if there is a SIGKILL that should be waking us up.
  * Called with the siglock held.
  */
-static int sigkill_pending(struct task_struct *tsk)
+static bool sigkill_pending(struct task_struct *tsk)
 {
-	return	sigismember(&tsk->pending.signal, SIGKILL) ||
-		sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
+	return sigismember(&tsk->pending.signal, SIGKILL) ||
+	       sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
 }
 
 /*