drm: add object property type

An object property is an id (idr) for a drm mode object.  This
will allow a property to be used set/get a framebuffer, CRTC, etc.

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --cc drivers/gpu/drm/drm_crtc.c
Simple merge

diff --cc include/drm/drm_crtc.h
Simple merge

diff --cc include/uapi/drm/drm_mode.h
Simple merge