bif: qpnp-bsi: disable BSI during master-disabled bus state

Disable the BSI PMIC peripheral when the bus state is changed
to master-disabled.  This can be used to save power when no
smart battery pack is detect.

Change-Id: Ic0ce8c11153a6bfa32e4661bf8d791265ebf4f95
Signed-off-by: David Collins <collinsd@codeaurora.org>