drm/msm/sde: set default bw to max bw in device tree

Current bandwidth is set to 6GB by default. This is too
low for some use cases. Change the default bandwidth to
maximum defined in device tree to support all use cases.
Default bandwidth is used if user mode control does provide
any override. Also, reduce the enable bandwidth to 2MB for
apps RSC.

CRs-Fixed: 2037879
Change-Id: I6a6b26a3c14bc40893d8aa57470fdac684d4ac31
Signed-off-by: Alan Kwong <akwong@codeaurora.org>