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/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 2e937a5..25a4a81 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -796,10 +796,7 @@
 	 * If there's no signal to deliver, we just put the saved sigmask
 	 * back.
 	 */
-	if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
-		current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
-		set_current_blocked(&current->saved_sigmask);
-	}
+	restore_saved_sigmask();
 }
 
 /*