feat(morello): implement methods to retrieve soc-id information

feat(morello): implement methods to retrieve soc-id information

Added silicon revision in the platform information SDS structure.

Implemented platform functions to retrieve the soc-id information
for the morello SoC platform. SoC revision, which is same as
silicon revision, is fetched from the morello_plat_info structure
and SoC version is populated with the part number from SSC_VERSION
register, and is reflected in bits[0:15] of soc-id.

Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>
Change-Id: I8e0c5b2bc21e393e6d638858cc2ea9f4638f04b9