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/gpio/gpio-pxa.c b/drivers/gpio/gpio-pxa.c
index 9cc108d..7523b6d 100644
--- a/drivers/gpio/gpio-pxa.c
+++ b/drivers/gpio/gpio-pxa.c
@@ -19,6 +19,7 @@
 #include <linux/init.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
+#include <linux/irqchip/chained_irq.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
@@ -26,8 +27,6 @@
 #include <linux/syscore_ops.h>
 #include <linux/slab.h>
 
-#include <asm/mach/irq.h>
-
 #include <mach/irqs.h>
 
 /*