soc: nordic: nrf54h: disable CAN120 MCAN cache

Configure CAN120 MCAN core registers as non-cachable to prevent D-Cache
from inhibiting volatile accesses to the CAN120 MCAN registers. Also
apply non-cachable attribute to the message ram region. Even though the
MCAN driver handles cache invalidation/flushing, MPU faults are still
triggered (to be investigated).

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>