clk: qcom: gdsc-regulator: add support to manage bus bandwidth requests

Add support to vote for bus bandwidth in GDSC regulator callback
functions.  This is needed for GDSC instances which access
registers via a bus that can be disconnected.

Change-Id: I8dff3d42eeed67230c81418ea9be88e81bdb44ce
Signed-off-by: David Collins <collinsd@codeaurora.org>