ARM: fix more fallout from 9f97da78bf (Disintegrate asm/system.h for ARM)

arch/arm/kernel/io.c: In function '_memcpy_toio':
arch/arm/kernel/io.c:29: error: implicit declaration of function 'outer_sync'
arch/arm/mach-omap2/omap_l3_noc.c: In function 'l3_interrupt_handler':
arch/arm/mach-omap2/omap_l3_noc.c💯 error: implicit declaration of function 'outer_sync'
kernel/irq/generic-chip.c: In function 'irq_gc_mask_disable_reg':
kernel/irq/generic-chip.c:45: error: implicit declaration of function 'outer_sync'
kernel/sched/rt.c: In function 'rt_set_overload':
kernel/sched/rt.c:248: error: implicit declaration of function 'outer_sync'
...

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-omap2/include/mach/barriers.h

@@ -22,6 +22,8 @@
 #ifndef __MACH_BARRIERS_H
 #define __MACH_BARRIERS_H
 
+#include <asm/outercache.h>
+
 extern void omap_bus_sync(void);
 
 #define rmb()		dsb()