ARM platforms: Provide SDEI entry point validation

Provide a strong definition for plat_sdei_validate_sdei_entrypoint()
which translates client address to Physical Address, and then validating
the address to be present in DRAM.

Change-Id: Ib93eb66b413d638aa5524d1b3de36aa16d38ea11
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
3 files changed