ARM: select CPU_CPU15_MMU/MPU appropriately

Currently CPU_V7 selects CPU_CP15_MMU, however in the case of a V7 CPU
implementing the PMSA, such as the Cortex-R7, the CP15_MMU operations are
not available. Selecting CPU_CP15_MPU is appropriate in this case.

This patch makes CPU_CP15_MMU dependent on the use of the MMU, selecting
CPU_CP15_MPU for v7 processors when !MMU is chosen.
Signed-off-by: Jonathan Austin <jonathan.austin@arm.com>

arch/arm/mm/Kconfig

@@ -392,7 +392,8 @@ config CPU_V7
 	select CPU_CACHE_V7
 	select CPU_CACHE_VIPT
 	select CPU_COPY_V6 if MMU
-	select CPU_CP15_MMU
+	select CPU_CP15_MMU if MMU
+	select CPU_CP15_MPU if !MMU
 	select CPU_HAS_ASID if MMU
 	select CPU_PABRT_V7
 	select CPU_TLB_V7 if MMU