drm/amdgpu/jpeg - skip change of power-gating state for sriov

Powergating is handled in the host driver.

Reviewed-by: Zhigang Luo <zhigang.luo@amd.com>
Signed-off-by: Samir Dhume <samir.dhume@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>