drm/amdgpu: Updated XGMI power down control support check

Updated SMC FW version check to determine if XGMI power down control is supported

Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>