msm: acpuclock-9615: Add bus scaling support

Scale bus bandwidth requests between EBI memory and the CPU
based on the CPU's clock rate. These request serve to improve
power by allowing the clocks on this path to decrease in rate
when the CPU is running slow and is not in need of low-latency
memory accesses, and to improve performance when the CPU is
running fast and memory accesses are a bottleneck.

Change-Id: Ife8fab910f7dc2ce6429bac6848f2475655023b9
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>