msm: mdss: reduce the bandwidth request calls by mdp3

Currently mdp3 is calling bus calls for bandwidth request
as soon as there is any change in new bandwidth value.
This extra communication is showing power issues.
Do not change the bw vote for solid fill case so that
this fluctuation is avoided.

Change-Id: I1d0a48a090bd1ac9321d08d67715e31036122060
Signed-off-by: Shivaraj Shetty <shivaraj@codeaurora.org>