msm: mdss: override DSI hw configuration

MSM8996/8994/8992 is configured for split display
configuration as default option. However, bootloader
can override this configuration to single dsi by
selecting a single dsi panel on one of controller
and set "none" to another controller. This requires
hardware override.

Change-Id: I3e585079548e92f6d576615059987321dfad132a
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>