feat(rmmd): el3-rmm ide key management interface

Patch introduces the EL3-RMM SMC Interface for Root Port
Key management as per RFC discussed here:
https://github.com/TF-RMM/tf-rmm/wiki/RFC:-EL3-RMM-IDE-KM-Interface

Three IDE Key management smc calls have been added:
 - RMM_IDE_KEY_PROG()
 - RMM_IDE_KEY_SET_GO()
 - RMM_IDE_KEY_SET_STOP()
 - RMM_IDE_KM_PULL_RESPONSE()

Due to the absence of root port support in FVP, we are
currently adding placeholders in this patch for the platform
APIs to return success irrespective of the arguments being passed
by the caller(Realms). The SMCs are guarded by
`RMMD_ENABLE_IDE_KEY_PROG` build flag and is disabled by default.
We expect that once the SMCs are stabilized, this build flag will
not be required anymore.

Change-Id: I9411eb7787dac2a207bd14710d251503bd9626ce
Signed-off-by: Sona Mathew <sonarebecca.mathew@arm.com>
10 files changed