msm: mdss: fix MDP hang when using 2 or more layers

Hang is seen when 2 or more overlapping layers are used in MDP, this is
caused by problem with VBIF dynamic clock gating. Bypass VBIF dynamic
clock gating and force clocks on to avoid MDP hang.

Change-Id: I369d036aa059f79c48f3b2feec8ca2b0f49dd301
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>