iommu: msm: Add bus voting to IOMMU driver

Add framework to enable IOMMU driver to vote for bus bandwidth. This
is required for some IOMMUs to allow certain clocks to turn on.
Bus voting will only be enabled if the corresponding IOMMU device
tree node has the appropriate bus bandwidth information specified.

Change-Id: If34e3f806e4b7674bf68e3fcc975e1d589450cc1
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>