fix error-path NULL deref in alloc_posix_timer()

Found by static checker (http://repo.or.cz/w/smatch.git).

Signed-off-by: Dan Carpenter <[e-mail]>
Acked-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/posix-timers.c

···
 		return tmr;
 	if (unlikely(!(tmr->sigq = sigqueue_alloc()))) {
 		kmem_cache_free(posix_timers_cache, tmr);
-		tmr = NULL;
+		return NULL;
 	}
 	memset(&tmr->sigq->info, 0, sizeof(siginfo_t));
 	return tmr;