boards: arm: fvp_baser_aemv8r_aarch32: enable ARM_MPU

Now that we have support for ARMv8-R MPU and static
mpu regions define at SoC level we can enable the ARM MPU.

Signed-off-by: Julien Massot <julien.massot@iot.bzh>
Signed-off-by: Manuel Arguelles <manuel.arguelles@nxp.com>