arm: Move chained_irq_(enter|exit) to a generic file

These functions have been introduced by commit 10a8c383 (irq: introduce
entry and exit functions for chained handlers) in asm/mach/irq.h. This
patch moves them to linux/irqchip/chained_irq.h so that generic irqchip
drivers do not rely on architecture specific header files.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>
diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index a32e0d5..0b1c0af 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -38,6 +38,7 @@
 #include <linux/interrupt.h>
 #include <linux/percpu.h>
 #include <linux/slab.h>
+#include <linux/irqchip/chained_irq.h>
 #include <linux/irqchip/arm-gic.h>
 
 #include <asm/irq.h>