msm: mdss: add bw requirement calculations for ppp on mdp3

Currently ppp engine adds huge fudge factors for bandwidth
calculations. Remove the fudge and add right bw requirement
calculations for the same.

Change-Id: I798d2bf6ac4c4cff13c82efdd53e5c73fa84b1ff
Signed-off-by: Shivaraj Shetty <shivaraj@codeaurora.org>