sde: Enable source split

Enable source split feature in display engine. A layer does not
qualify for source split if source or destination width exceeds
the max pipe width. Even if "always_src_split" is enabled, program
2 pipes only if source width exceeds left-split or the pipe clock
exceeds mixer clock. It is required for perf/power optimization.

Change-Id: I9e53f43562f2187b17c61232b8a471a5a0f75423
3 files changed