[POWERPC] Move xmon_irq() declaration into xmon.h

The typdef for irqreturn_t was moved into its own header a
while back, so there's no reason we can't move xmon_irq()
into xmon.h now.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/xmon.h b/include/asm-powerpc/xmon.h
index 81477f2..d83da3c 100644
--- a/include/asm-powerpc/xmon.h
+++ b/include/asm-powerpc/xmon.h
@@ -12,11 +12,14 @@
 
 #ifdef __KERNEL__
 
+#include <linux/irqreturn.h>
+
 #ifdef CONFIG_XMON
 extern void xmon_setup(void);
 extern void xmon_register_spus(struct list_head *list);
 struct pt_regs;
 extern int xmon(struct pt_regs *excp);
+extern irqreturn_t xmon_irq(int, void *);
 #else
 static inline void xmon_setup(void) { };
 static inline void xmon_register_spus(struct list_head *list) { };