ARM: 7115/4: move __exception and friends to asm/exception.h

The definition of __exception_irq_entry for
CONFIG_FUNCTION_GRAPH_TRACER=y needs linux/ftrace.h, but this creates a
circular dependency with it's current home in asm/system.h. Create
asm/exception.h and update all current users.

v4:	- rebase to rmk/for-next
v3:	- remove redundant includes of linux/ftrace.h
v2:	- document the usage restricitions of __exception*

Cc: Zoltan Devai <zdevai@gmail.com>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-pxa/irq.c b/arch/arm/mach-pxa/irq.c
index b09e848..ca60757 100644
--- a/arch/arm/mach-pxa/irq.c
+++ b/arch/arm/mach-pxa/irq.c
@@ -19,6 +19,8 @@
 #include <linux/io.h>
 #include <linux/irq.h>
 
+#include <asm/exception.h>
+
 #include <mach/hardware.h>
 #include <mach/irqs.h>
 #include <mach/gpio.h>