um: Fix get_signal() usage

If get_signal() returns us a signal to post
we must not call it again, otherwise the already
posted signal will be overridden.
Before commit a610d6e672 this was the case as we stopped
the while after a successful handle_signal().

Cc: <stable@vger.kernel.org> # 3.10-
Fixes: a610d6e672 ("pull clearing RESTORE_SIGMASK into block_sigmask()")
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/kernel/signal.c

@@ -69,7 +69,7 @@ void do_signal(struct pt_regs *regs)
 	struct ksignal ksig;
 	int handled_sig = 0;
 
-	while (get_signal(&ksig)) {
+	if (get_signal(&ksig)) {
 		handled_sig = 1;
 		/* Whee!  Actually deliver the signal.  */
 		handle_signal(&ksig, regs);