msm: mdss: cleanup MDP3 driver compilation

Enable MDP3 driver compilation only on chip-sets where MDP3 core is
present. This helps reduce the size of kernel binary where MDP3 is
not present.

Change-Id: I357ff73f91e7ee1654a8666a78efebf68a2a8290
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>