Make enablement of the MMU more flexible

This patch adds a 'flags' parameter to each exception level specific function
responsible for enabling the MMU. At present only a single flag which indicates
whether the data cache should also be enabled is implemented. Subsequent patches
will use this flag when enabling the MMU in the warm boot paths.

Change-Id: I0eafae1e678c9ecc604e680851093f1680e9cefa
diff --git a/plat/fvp/aarch64/fvp_common.c b/plat/fvp/aarch64/fvp_common.c
index 3fe3a21..3926239 100644
--- a/plat/fvp/aarch64/fvp_common.c
+++ b/plat/fvp/aarch64/fvp_common.c
@@ -119,7 +119,7 @@
 		mmap_add(fvp_mmap);					\
 		init_xlat_tables();					\
 									\
-		enable_mmu_el##_el();					\
+		enable_mmu_el##_el(0);					\
 	}
 
 /* Define EL1 and EL3 variants of the function initialising the MMU */