drm/msm/dsi-staging: enable DSI command DMA scheduling

From HW version 2.2 onwards DSI controller supports scheduling
of DMA command transfer feature, where SW can program on which
vertical blanking line command trigger should happen. This change
adds support for the same in video mode panels.

Change-Id: Idfd52d20d594ff14b9ccc2e4f40e5abd67c457ee
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>