soc: nxp: s32k3: fix erratum ERR011573

Due to erratum ERR011573, speculative accesses might be performed
to normal memory unmapped in the MPU. This can be avoided by using
MPU region 0 to cover all unmapped memory and make this region
execute-never and inaccessible.

Fixes #89852

Co-authored-by: Peter van der Perk <peter.vanderperk@nxp.com>
Signed-off-by: Manuel Argüelles <manuel.arguelles@nxp.com>