ARM: dts: msm: Enable DSC merge topology for sdmmagpie target

Changes display-topology to 2 mixers, 2 encoders and 1 interface
for QHD+ command and QHD+ video mode.

Change-Id: I447f7df9b61fd121404679c91a8f9f22b6642663
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>