msm: msm_bus: Introduce new debug module to set bus clocks

Introduce a new module to allow clients to set a floor vote on bus clocks
either using an API or via sysfs interface. Clients are still always
recommended to use standard bus scaling APIs , these new APIs are a debug
feature and a meant for debugging system performance issues.

Change-Id: I7688e391413c23d9024a7b525f60c90f317d0847
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>