drm/msm/dsi-staging: update phy timings when clock is overridden

Currently in dsi driver when dsi bit clock is overridden via
device tree property, then driver is not updating the phy timings
accordingly. This change fixes the same.

Change-Id: I64ebfb4c3ff5b621449c9e5fcbc9212fadca272c
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>