msm: mdss: Fix ib value calculations for multiple AXI masters

When multiple AXI masters are used by MDP, Instantaneous Bandwidth (ib)
should not be divided by number of masters. Arbitrated Bandwidth (ab)
is the only factor which should change based on the number of masters.
Fix this by removing IB division in the calculations.

Change-Id: Ieedddede2d72a1503805655b863a84bf96b52944
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>