wait_task_stopped/continued: remove unneeded p->signal != NULL check

The child was found on ->children list under tasklist_lock, it must have a
valid ->signal. __exit_signal() both removes the task from parent->children
and clears ->signal "atomically" under write_lock(tasklist).

Remove unneeded checks.

Signed-off-by: Oleg Nesterov <[e-mail]>
Acked-by: Roland McGrath <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/exit.c

···
 	if (!p->exit_code)
 		return 0;
 	if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
-	    p->signal && p->signal->group_stop_count > 0)
+	    p->signal->group_stop_count > 0)
 		/*
 		 * A group stop is in progress and this is the group leader.
 		 * We won't report until all threads have stopped.
···
 	int retval;
 	pid_t pid;
 	uid_t uid;
-
-	if (unlikely(!p->signal))
-		return 0;
 
 	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
 		return 0;