drm/amd/powerplay: add function to start thermal control

Add function to start thermal control for smu11 when smu hw_init.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>