msm: mdss: Fix ctl flush bits reset by dspp programming

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.

Starting for Ia510fc6377c5b328cb4225a4725275d86b72dbff, ctl
flush bits were getting reset. Fix this in case mixer is
setup again with borderfill.

Change-Id: I12f60472e8f0f5630e239fb4b4026fda0d2f7cba
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
Signed-off-by: Harsh Sahu <hsahu@codeaurora.org>