drmdoc: update docs from upstream
drmdoc: stop accumulating content if indentation is missing

When indentation is missing, that means the docs for the prop are
finished. DRM docs often contain free-form paragraphs between prop docs.
drmdoc: sort props by name

This ensures the output order is deterministic.
drmdoc: use go/format to format generated files
Add descriptions to filter links
Add driver filter to device list
Enable cache header
Display kernel docs on prop page
drmdoc: new package
Remove extraneous parentheses
Add object type filter to properties list
Add missing drm.go
Check property types consistency
Merge all property specs
Update dependencies
Fix property page with no supporting driver
drmtree: handle USB devices

References: https://github.com/ascent12/drm_info/pull/49
Add tooltip with format/modifier hex code in /formats