drm/amd/powerplay: implement VCN power gating control interface

VCN Gate/Ungate by processing the SMU power up/down message, otherwise
S3 will resume failed as JPEG always power off during start VCN stage.

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>