msm_fb: mdss: Add EDP physical layer configuration support

Add code to configure the enable/disable and PLL settings
for the physical layer of EDP.

Change-Id: I6e15e41fdd23cc5a4855a3addf85050ade802d8d
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>
Signed-off-by: Asaf Penso <apenso@codeaurora.org>