msm: msm_bus: Introduce new dynamic throttling scheme

Introduce a new dynamic throttling scheme for certain "non-real time"
masters based on the available bus bandwidth and the currently voted
bandwidth requirements of some "real time" masters.

Change-Id: Icf019f89bbe2425c706f2fc49884f41110a78299
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>