Add flags AMD_CG_SUPPORT_SDMA_MGCG for Vangogh.
Start to open sdma mgcg from firmware version 70.
Signed-off-by: NJinzhou Su <Jinzhou.Su@amd.com>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>