[ARM] footbridge: add isa_init_irq() to common header

isa_init_irq() is defined in arch/arm/mach-footbridge/isa-irq.c
and used in arch/arm/mach-footbridge/common.c but there is no
definition in any header. Move the definition in common.c to
common.h to stop the sparse warning:

isa-irq.c:118:13: warning: symbol 'isa_init_irq' was not declared.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

arch/arm/mach-footbridge/common.c

@@ -28,8 +28,6 @@
 
 #include "common.h"
 
-extern void __init isa_init_irq(unsigned int irq);
-
 unsigned int mem_fclk_21285 = 50000000;
 
 EXPORT_SYMBOL(mem_fclk_21285);

arch/arm/mach-footbridge/common.h

@@ -7,3 +7,4 @@ extern void isa_rtc_init(void);
 extern void footbridge_map_io(void);
 extern void footbridge_init_irq(void);
 
+extern void isa_init_irq(unsigned int irq);

arch/arm/mach-footbridge/isa-irq.c

@@ -28,6 +28,8 @@
 #include <asm/irq.h>
 #include <asm/mach-types.h>
 
+#include "common.h"
+
 static void isa_mask_pic_lo_irq(unsigned int irq)
 {
 	unsigned int mask = 1 << (irq & 7);