drm/amdgpu/swsmu: add smu support for dimgrey_cavefish(v2)

Reuse sienna_cichlid pp table for dimgrey_cavefish.

v2: update related comment.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>