disp: msm: dp: add eDP support as a primary display

Add support for new eDP interface. As the protocol is similar to DP,
the new eDP driver shall re-use the DP functionality wherever applicable.

Change-Id: I0bcaa2bf2c401cbfb3470ecf232bf6643fb43a7d
Signed-off-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com>
Signed-off-by: Nilesh Laad <quic_nlaad@quicinc.com>