arch: arm: Changes to avoid warnings during compilation

Changes to avoid warnings for enabling Werror flag.

Change-Id: I1d5c5c90a6a6f7a5c20730997300bc89d9e0908b
diff --git a/arch/arm/mmu.c b/arch/arm/mmu.c
index 2027b41..d50c43a 100644
--- a/arch/arm/mmu.c
+++ b/arch/arm/mmu.c
@@ -27,6 +27,7 @@
 #include <arch/arm.h>
 #include <arch/defines.h>
 #include <arch/arm/mmu.h>
+#include <platform.h>
 
 #if ARM_WITH_MMU