msm: mdss: add support for destination split

MDSS 1.8.0 supports split mux with which we can
support resolution of 2k driving both the interfaces
on single control path.

Add support for both video mode and command mode
interfaces

Change-Id: I40b6a66a9cb0b7a62fb269e31300df22e9b7cff9
Signed-off-by: Kalyan Thota <kalyant@codeaurora.org>