drm/msm/dsi-staging: update PHY configuration to support cphy

Add support to read cphy boolean flag from panel dtsi
and configure DSI PHY registers accordingly. Update
bit/byte clock calculation according to cphy specifications.
Update clock parents so that the relevant divider blocks
are configured to support cphy.

Change-Id: Iaca61eec01a488657b086f59910c52f8c79e26a4
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>