ARM: outer cache: add WARN_ON() to outer_disable()

Add WARN_ON() conditions to outer_disable() to ensure that its
requirements aren't violated.

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

arch/arm/mm/Makefile

@@ -95,6 +95,7 @@ obj-$(CONFIG_CPU_V7M)		+= proc-v7m.o
 AFLAGS_proc-v6.o	:=-Wa,-march=armv6
 AFLAGS_proc-v7.o	:=-Wa,-march=armv7-a
 
+obj-$(CONFIG_OUTER_CACHE)	+= l2c-common.o
 obj-$(CONFIG_CACHE_FEROCEON_L2)	+= cache-feroceon-l2.o
 obj-$(CONFIG_CACHE_L2X0)	+= cache-l2x0.o
 obj-$(CONFIG_CACHE_XSC3L2)	+= cache-xsc3l2.o