msm: mdss: Parse max bandwidth property from device tree

Maximum bandwidth on the AXI bus supported by MDSS is a hardware
capability that needs to be exposed to userspace process via
sysfs node for MDP composition decisions.

Change-Id: I60e74e96666ca97f21a9880f49a95c3264d01870
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@codeaurora.org>
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>