msm: mdss: increase bus scaling factor to improve performance

Fix performance issues seen with different use cases such as HDMI and
MDP composition by increasing bus scaling factor used.

CRs-Fixed: 398503
Change-Id: I2391f81c0cba1fa7f5849ce55ec89762765d7575
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>