MLK-18619: [MX8MM-EVK]CSU_RDC: enable csu_rdc test in ATF make the board crash

csu_rdc test in ATF makes use of GPIO 4 and 5. Unfortunatly GPIO5 is
being used by u-boot. This is why u-boot crashes.
Changing the peripherals to protect, instead of gpio4 and 5, use csu
and rdc registers instead.

Signed-off-by: Silvano di Ninno <silvano.dininno@nxp.com>
Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
(cherry picked from commit fe1cd0abc6c57cc59312ab751dd015cb149d7100)