drm/atomic: Make private objs proper objects

drm/atomic: Make private objs proper objects

Make the atomic private object stuff less special by introducing proper
base classes for the object and its state. Drivers can embed these in
their own appropriate objects, after which these things will work
exactly like the plane/crtc/connector states during atomic operations.

v2: Reorder to not depend on drm_dynarray (Daniel)

Change-Id: I475f3c46440934b8d6f461935b6413624b7d34c7
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> #v1
Signed-off-by: Ville Syrj?l? <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170712155102.26276-3-ville.syrjala@linux.intel.com
Signed-off-by: Ao Xu <ao.xu@amlogic.com>