arch: arm: aarch32: add ARMv8-R MPU support

ARMv8-R aarch32 processor has support for
ARM PMSAv8-32. To add support for ARMv8-R we reuse the
ARMv8-M effort and change access to the different registers
such as rbar, rlar, mair, prselr.

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