This goes all the way back to the original KMS commit aeons ago

commit f453ba04
Author: Dave Airlie <airlied@redhat.com>
Date:   Fri Nov 7 14:05:41 2008 -0800

    DRM: add mode setting support

But it seems to be completely unused. Only i915 and nouveau even
register these properties, and the corresponding DDX don't even look
at them. Also the sysfs files are read-only, so not useful to
configure anything.

I suspect that this was added with the goal to have read-only access
to all properties in sysfs, but we never followed through on that.
Also, that should be done in a more generic fashion.

Since it would be real work to fix up the locking (with atomic we're
now chasing pointers when reading properties) and it seems unused lets
just nuke this all. It's easier. Of course we'll keep the properties
themselves, those are still exposed through the KMS ioctls.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459331120-27864-5-git-send-email-daniel.vetter@ffwll.ch