ArmPkg: Add initial OpteeLib implementation

This is initial version of OP-TEE library that provides api's to
communicate with OP-TEE OS (Trusted OS based on ARM TrustZone) via
secure monitor calls. Currently it provides basic api to detect OP-TEE
presence via UID matching.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>