disp: msm: dsi: update the threshold time based on panel jitter

Minimum threshold time is sum of panel jitter time, prefill lines time
and buffer time of 100usec. For panels with high jitter, we can cross the
default threshold time. Update the calculation to accommodate high jitter
panels in calculating dsi clocks.

Change-Id: I93163a07c7d0b51eb3704609b4efed6c1e277761
Signed-off-by: Vara Reddy <varar@codeaurora.org>