drm_hwcomposer: fill hwc_display_contents retireFenceFd

This restores the behavior of "drm_hwcomposer: Populate retireFenceFd"

The retire fence is triggered when all releaseFenceFd's of the display's
layers are triggered.

Change-Id: Id06f2df03dcb9638ccbae23f46c42b05551fae6d
1 file changed