msm: msm_bus: Add support for master clocks

Add support for master clocks on bus nodes. Induvidual
nodes may have clocks associated with them which need to be
aggregated in addition to the bus clocks they connect to.

Change-Id: Idd268587f6558738680390d3f22fc9c9ceb7af91
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>