core: introduce libefi for StandaloneMm

According to Platform Initialization (PI) Specification [1] and
Discussion on edk2 mailing list [2],
StandaloneMm shouldn't create Hob but it should be passed

core: introduce libefi for StandaloneMm

According to Platform Initialization (PI) Specification [1] and
Discussion on edk2 mailing list [2],
StandaloneMm shouldn't create Hob but it should be passed from TF-A.
That's why StandaloneMm in Arm wouldn't produce Hob by itself [3] but
other software stack should pass boot information via PHIT Hob.

This patch introduces libefi including create Hob to deliver
boot information to StandaloneMm and defines related data structures.

Link: https://uefi.org/sites/default/files/resources/PI_Spec_1_6.pdf [1]
Link: https://edk2.groups.io/g/devel/topic/103675962#114283 [2]
Link: https://github.com/tianocore/edk2/pull/6116 [3]

Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Levi Yun <yeoreum.yun@arm.com>

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