usermodehelper: ____call_usermodehelper() doesn't need do_exit()

Minor cleanup.  ____call_usermodehelper() can simply return, no need to
call do_exit() explicitely.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 5b9bd473)
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

kernel/kmod.c

@@ -231,13 +231,6 @@ static int ____call_usermodehelper(void *data)
 	return 0;
 }
 
-static int call_helper(void *data)
-{
-	/* Worker thread started blocking khelper thread. */
-	kmod_thread_locker = current;
-	return ____call_usermodehelper(data);
-}
-
 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
 {
 	if (info->cleanup)