[ARM] Fix circular include dependency with IRQ headers

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
index 11dcd52..f88efb1 100644
--- a/arch/arm/kernel/irq.c
+++ b/arch/arm/kernel/irq.c
@@ -38,6 +38,7 @@
 #include <linux/proc_fs.h>
 
 #include <asm/system.h>
+#include <asm/mach/irq.h>
 #include <asm/mach/time.h>
 
 /*