ARM: 8920/1: share get_signal_page from signal.c to process.c

The get_signal_page() function is defined in signal.c and used in
process.c but there is no shared definition. Add one in signal.h to
silence the following warning:

arch/arm/kernel/signal.c:683:13: warning: symbol 'get_signal_page' was not declared. Should it be static?
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/kernel/process.c

@@ -36,6 +36,8 @@
 #include <asm/tls.h>
 #include <asm/vdso.h>
 
+#include "signal.h"
+
 #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
 #include <linux/stackprotector.h>
 unsigned long __stack_chk_guard __read_mostly;

arch/arm/kernel/signal.h

@@ -9,3 +9,5 @@ struct rt_sigframe {
 	struct siginfo info;
 	struct sigframe sig;
 };
+
+extern struct page *get_signal_page(void);