drm/amd/pm: Rename pmfw message SetPstatePolicy

Rename pmfw message SelectPstatePolicy to SetThrottlingPolicy as per
pmfw interface header for smu_v_13_0_6

Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>