ARM: dts: msm: change topology for truly qhd dsc panels on SDM845

Change the default topology to use dual layermixer and dsc merge config
for truly qhd command and video mode dsc panels.

Change-Id: I1d13e6e0dfbc8e246d37349d765e710a3c8f8bb5
Signed-off-by: Vara Reddy <varar@codeaurora.org>