msm: mdss: cleanup eDP driver compilation

Enable eDP driver compilation only on chip-sets where eDP core is
present. This helps reduce the size of kernel binary where eDP
controller is not present.

Change-Id: I2f201e3258b2b8f2ea224a6d0873852551bf1527
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>