drm/amdgpu/VCN2.0: remove powergating for UVDW tile

No UVDW tile any more from VCN2.0, so mark out related fields.

It fixes error:
"[drm] Register(0) [mmUVD_PGFSM_STATUS] failed to reach value 0x002aaaaa != 0x00aaaaaa"

Signed-off-by: Leo Liu <leo.liu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>