Find that ring sdma0 test failed if turn on SDMA powergating after do
mode2 reset.

Perhaps the mode2 reset does not reset the SDMA PG state, SDMA is
already powered up so there is no need to ask the SMU to power it up
again. So I skip this function for a moment.
Signed-off-by: chen gong <curry.gong@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>