drm/amdgpu/powerplay: add initial swSMU support for sienna_cichlid (v2)

SMU11 based similar to navi1x.

v2: squash in SMU IF updates

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>