new helper: restore_saved_sigmask()

first fruits of ..._restore_sigmask() helpers: now we can take
boilerplate "signal didn't have a handler, clear RESTORE_SIGMASK
and restore the blocked mask from ->saved_mask" into a common
helper.  Open-coded instances switched...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
index f79d4b8..62b3493 100644
--- a/arch/tile/kernel/signal.c
+++ b/arch/tile/kernel/signal.c
@@ -350,10 +350,7 @@
 	}
 
 	/* If there's no signal to deliver, just put the saved sigmask back. */
-	if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
-		current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
-		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
-	}
+	restore_saved_sigmask();
 
 done:
 	/* Avoid double syscall restart if there are nested signals. */