msm_fb: mdss: Add eDP controller driver support

eDP controller is one of the output interfaces for MDSS.
Add support for eDP host controller driver which runs in
Video mode only and eDP related changes for msm_fb panel driver.

Change-Id: I0a150f8d712f57bdfaee9051b2893e2910195567
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Ravishangar Kalyanam <rkalya@codeaurora.org>
Signed-off-by: Asaf Penso <apenso@codeaurora.org>
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>