[ARM] Fix fallout from IRQ regs changes

Some ARM platforms were still broken as a result of the IRQ register
passing changes, mostly due to a missing linux/irq.h include.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-footbridge/dc21285.c b/arch/arm/mach-footbridge/dc21285.c
index fa5d497..1463330 100644
--- a/arch/arm/mach-footbridge/dc21285.c
+++ b/arch/arm/mach-footbridge/dc21285.c
@@ -16,6 +16,7 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/ioport.h>
+#include <linux/irq.h>
 
 #include <asm/io.h>
 #include <asm/irq.h>