Merge UEFI Variable Authentication support
This feature adds support for protecting UEFI variables from tampering
using cryptographic means as defined by the standard.
If the feature is enabled the SmmGW SP can rely on the PSA-Crypto SP to
execute cryptographic operations or alternatively a crypto library
instance can be hosted in the SP.
For implementation details please refer to the updated documentation.
Change-Id: I0686834166dac50cb4ea97bcd1d232e0ca271d48
Signed-Off-By: Gyorgy Szing <gyorgy szing@arm.com>