drm/msm/sde: adding implementation for mdp_top in hw driver

Add mdp_top block support to hw layer, provides split pipe
control, and interface select. Use mdp_top from intf block
to program interface select.

Change-Id: I15f2070f7d552a6ec11bda0302f362e22ca6e84e
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>
Signed-off-by: Krishna Srinivas Kundurthi <kskund@codeaurora.org>