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/h8300/kernel/signal.c b/arch/h8300/kernel/signal.c
index e58992a..63623da 100644
--- a/arch/h8300/kernel/signal.c
+++ b/arch/h8300/kernel/signal.c
@@ -501,8 +501,7 @@
 	}
 
 	/* If there's no signal to deliver, we just restore the saved mask.  */
-	if (test_and_clear_thread_flag(TIF_RESTORE_SIGMASK))
-		set_current_blocked(&current->saved_sigmask);
+	restore_saved_sigmask();
 }
 
 asmlinkage void do_notify_resume(struct pt_regs *regs, u32 thread_info_flags)