msm: kgsl: Add bus scale setting support to speed config

This change helps driver to load dynamic bus scale settings
based on the speed configuration. This is an additional support
to spped config along with the GPU Power Level settings.

Change-Id: Ia797dc2fc3e7742ad66c38532623442210356c66
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>