add sdma firmware load support for soc model

v2: drop some emulator leftovers (Alex)
Signed-off-by: NKevin Wang <kevin1.wang@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NLe Ma <Le.Ma@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>