semaphore: __down_common: use signal_pending_state()

Change __down_common() to use signal_pending_state() instead of open
coding.

The changes in kernel/semaphore.o are just artifacts, the state checks are
optimized away.

Signed-off-by: Oleg Nesterov <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Roland McGrath <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/semaphore.c

···
 	waiter.up = 0;
 
 	for (;;) {
-		if (state == TASK_INTERRUPTIBLE && signal_pending(task))
-			goto interrupted;
-		if (state == TASK_KILLABLE && fatal_signal_pending(task))
+		if (signal_pending_state(state, task))
 			goto interrupted;
 		if (timeout <= 0)
 			goto timed_out;