msm: kgsl: Modernize bus scaling

Replace all of the legacy bus scaling code with the new interconnect API.
This includes removing all msm_bus support as well as the devbw interface
which is not needed since icc can set both the IB and the AB on our behalf.

As part of this, move most of the bus specific code into its own file,
add support for parsing a table of our own from the device tree and handle
both the GPU and GMU bus setting paths properly.

Change-Id: Ic0dedbadfbb3c48ec414ec60e3032b2204b4e724
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>