drm: msm: dsi-staging: add support for dfps

Added support for dynamic fps change and to
enable/disable timing db during fps update along
with necessary logic to update fps. It also includes
updating the new fps mode in the connector probed list.

Change-Id: I10fd7f4388d1617b91251b06e67a8c05e1d2f54d
Signed-off-by: Raviteja Tamatam <travitej@codeaurora.org>