drm/amd/powerplay: add new smu9_driver_if.h for vega12 (v2)

Add driver firmware interface header.

v2: squash in interface updates.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>