drm/amdgpu: cleanup MES12 command submission

drm/amdgpu: cleanup MES12 command submission

The approach of having a separate WB slot for each submission doesn't
really work well and for example breaks GPU reset.

Use a status query packet for the fence update instead since those
should always succeed we can use the fence of the original packet to
signal the state of the operation.

While at it cleanup the coding style.

Fixes: ade887c63394 ("drm/amdgpu/mes12: Use a separate fence per transaction")
Reviewed-by: Mukul Joshi <mukul.joshi@amd.com>
Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>