Add interface to load, unload, invoke command for
secure display TA.

v2: Add debugfs interface for secure display TA
v3: fix warning in copy_from_user (Alex)
Signed-off-by: Jinzhou.Su <Jinzhou.Su@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>