drm/msm/dsi-staging: Add support for dynamically switch dsi clock

Add changes to support dynamic switching of dsi clock feature for
phy ver 2.0. This helps to avoid RF interference with DSI clock.

Change-Id: I69958d9224665296cc0f272e39dcdfcefbe293d4
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>