feat(measured-boot): add measured boot drivers

Introduces core measured boot support, including TPM event log handling,
hashing infrastructure, and event formatting per TCG spec. The driver is
imported from the existing implementation in TF-A.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: Ib2e6a88c86f110f9a6907c3e6dbb0dc736486de9
11 files changed