drm/msm/dsi-staging: add split link panel support in dsi driver

In split link panels, the four data lanes are split into
sublinks and the clock lane is shared among these sublinks.
This change adds support for split link panels in dsi driver.

Change-Id: Idde0d759130aa0a081852f4639224360d3b63142
Signed-off-by: Tharun Raj Soma <tsoma@codeaurora.org>