msm: mdss: ensure ctl flush in case of fence timeout

In the current composition cycle, if the staging params are
not changed, then currently MDP flush register is not configured.
But due to any unforeseen reason if MDP fence timeout happens then
to handle it gracefully we stage border fill. In this regard as
the mixer config has now changed, then ctl flush has to be set.

Change-Id: I24b9cb28426f8829ac3bb36bfa32859b588d06fd
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>