drm/msm/sde: add support for DisplayPort

Get DisplayPort's instance and configure DRM specific
modules like bridges and connectors to initialize the
DisplayPort driver.

Change-Id: I786ba7636818b8e59fbcd1e3e5b04012b87de090
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>