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/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index bfc3ec1..0f4cc67 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -132,12 +132,8 @@
 	check_syscall_restart(regs, &ka, signr > 0);
 
 	if (signr <= 0) {
-		struct thread_info *ti = current_thread_info();
 		/* No signal to deliver -- put the saved sigmask back */
-		if (ti->local_flags & _TLF_RESTORE_SIGMASK) {
-			ti->local_flags &= ~_TLF_RESTORE_SIGMASK;
-			sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
-		}
+		restore_saved_sigmask();
 		regs->trap = 0;
 		return 0;               /* no signals delivered */
 	}