backend/tdm: Add ds_tdm_output_hwc

backend/tdm: Add ds_tdm_output_hwc

ds_tdm_output_hwc composites surface or buffer if hardware layer of output
can use direct scan-out(bypass compositing at output buffer).

ds_tdm_output_hwc has is consists of ds_tdm_output_hwc_window.
for using hardware compositing, display-server should set compositing
infomation of ds_tdm_output_hwc_window

it would be nice to ds_tdm_output_hwc can display all ds_tdm_output_hwc_window
by direct scan-out but it has restrictions.
output has limited number of hardware layer and hardware layer has
hw restrictions(buffer size, transform, format, etc).
if ds_tdm_output_hwc_window can not be display by direct scan-out,
display-server should composite it at output buffer.

ds_tdm_output_hwc_window is updated at output when ds_output_hwc_validate and
ds_output_commit is called because ds_tdm_output_hwc is component of ds_output.

Change-Id: If78e862e4acbcc1ae465fe8315fc478f888657b3