msm: msm_bus: add regulator voting as part of sbm disconnect

There may be a scenario where a client is holding a non zero bandwidth
vote on a target slave config device, but have removed their vote
on the respective multimedia GDSC and MMCX. This can be problematic
when MMCX is collapsed but the config slave is still connected creating
a window where a faulty transaction to collapsed slave can be difficult
to diagnose. This can be prevented by holding a vote on MMCX as part of
the bandwidth vote to the multimedia config slave.

Change-Id: I7e26ab7e036cc064f1c9092783c99eb1666399ef
Signed-off-by: David Dai <daidavid1@codeaurora.org>