drm/msm/dp: clean up EDID and audio functionality

Clear the EDID memory allocated during DisplayPort cable
connection to avoid memory leaks. Furthermore, encapsulate
edid APIs in panel module only for a cleaner interface
and align audio module API naming with DisplayPort driver.

CRs-Fixed: 2128730
Change-Id: Idd89bff8b62dc3c6bb4c529097d75b29ee5b855e
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>