drm/amdgpu/gfx10: change register configure for sienna_cichlid

Update sienna_cichlid register configuration for sienna_cichlid
to match the update of header files.

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