drm/amd/powerplay: remove uvd_gated/vce_gated from smu_power_context (v2)

It's not needed for navi.

v2: remove unused variable (Alex)

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>