drm/amd/amdgpu: power up sdma engine when S3 resume back

The sdma_v4 should be ungated when the IP resume back,
otherwise it will hang up and resume time out error.

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>