drm/amdgpu: Fix vce initialize failed on Kaveri/Mullins

Forgot to add vce pg support via smu for Kaveri/Mullins.

Fixes: 561a5c83eadd ("drm/amd/pp: Unify powergate_uvd/vce/mmhub
                       to set_powergating_by_smu")

v2: refine patch descriptions suggested by Michel

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>