[ARM] Fix second missing declaration of cache_is_vivt()

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/include/asm-arm/mmu_context.h b/include/asm-arm/mmu_context.h
index 57b8def8..3d4b810 100644
--- a/include/asm-arm/mmu_context.h
+++ b/include/asm-arm/mmu_context.h
@@ -13,6 +13,7 @@
 #ifndef __ASM_ARM_MMU_CONTEXT_H
 #define __ASM_ARM_MMU_CONTEXT_H
 
+#include <asm/cacheflush.h>
 #include <asm/proc-fns.h>
 
 #if __LINUX_ARM_ARCH__ >= 6