drm/sde: add bridge chip support for drm driver

Display Bridgechip Abstration layer is a common framework to support
different kind of bridge chips with multi client accessing. This
change is to add a DRM bridge driver and hook it up with DBA
framework.

Change-Id: Ie225a7cdb55a4982199c1735c37986950c5fad05
Signed-off-by: Jin Li <jinl@codeaurora.org>