um: Fix do_signal() prototype

Once x86 exports its do_signal(), the prototypes will clash.

Fix the clash and also improve the code a bit: remove the
unnecessary kern_do_signal() indirection. This allows
interrupt_end() to share the 'regs' parameter calculation.

Also remove the unused return code to match x86.

Minimally build and boot tested.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/67c57eac09a589bac3c6c5ff22f9623ec55a184a.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/um/kernel/signal.c b/arch/um/kernel/signal.c
index 4f60e4a..57acbd6 100644
--- a/arch/um/kernel/signal.c
+++ b/arch/um/kernel/signal.c
@@ -64,7 +64,7 @@
 	signal_setup_done(err, ksig, singlestep);
 }
 
-static int kern_do_signal(struct pt_regs *regs)
+void do_signal(struct pt_regs *regs)
 {
 	struct ksignal ksig;
 	int handled_sig = 0;
@@ -110,10 +110,4 @@
 	 */
 	if (!handled_sig)
 		restore_saved_sigmask();
-	return handled_sig;
-}
-
-int do_signal(void)
-{
-	return kern_do_signal(&current->thread.regs);
 }