msm_fb: display: balance bus bandwidth on mdp axi port0 and port1

mdp read and write clients are connected on both mdp port0 and port1,
however, the bus bandwidth request is made on only port0. This change
divides mdp bw requests to port0 and port1 based on pipe connections
to mdp ports.
ab - no scaling factor - port0 and port1 split
ib - scaling factor - port 0 and port1 split

Change-Id: I9050d1178f634ca908675fa826d08bee09e2a2f3
Signed-off-by: Huaibin Yang <huaibiny@codeaurora.org>