MdePkg/ArmTrngLib: Definition for Arm TRNG library class interface

MdePkg/ArmTrngLib: Definition for Arm TRNG library class interface

Bugzilla: 3668 (https://bugzilla.tianocore.org/show_bug.cgi?id=3668)

The NIST Special Publications 800-90A, 800-90B and 800-90C
provide recommendations for random number generation. The
NIST 800-90C, Recommendation for Random Bit Generator (RBG)
Constructions, defines the GetEntropy() interface that is
used to access the entropy source. The GetEntropy() interface
is further used by Deterministic Random Bit Generators (DRBG)
to generate random numbers.

The Arm True Random Number Generator (TRNG) library defines an
interface to access the entropy source on a platform, following
the 'Arm True Random Number Generator Firmware Interface'
specification.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>