ARM: stm32mp: correctly handle Silicon revision

ARM: stm32mp: correctly handle Silicon revision

Handle correctly the silicon revision = REV_ID[15:0] of Device Version
and the associated device marking, A to Z on STMicroelectronics STM32MP
SOCs.

This patch prepare the introduction of next STM32MP family,
with STM32MP13x Rev.Z for REV_ID = 1.1.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>