msm: mdss: modularize DSC code to support 4K DSC split-panel

Display Steam Compression (DSC) use-cases requires parameter calculations
that affect MDP and DSI separately. Current implementation is not modular
and calculates all the parameters in one big subroutine. Due to this, an
issue has occurred where parameters that affect DSI relies on picture
width where as DSI parameters should be calculated only based on
uncompressed width to a particular DSI controller.

Also current MDP driver tries to service DSC setup for all different
topologies in a single subroutine and has become very error prone.
Modularize MDP DSC setup so that it is easy to maintain and also add
support for partial update for 4K DSC split-panel.

Change-Id: I7057e6a5a22a72a9a216e5bc9f7f946675bfbbb8
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>