Bluetooth: add support for controlling regulator s5a for hastings

Dymanically controlling of regulator s5a is to save power
consumption of hastings. That is to say, this regulator shall
be turned off when they are not used.

Change-Id: Ic8e43a2ce027c9160a763fb9a480ac7f2575437f
Signed-off-by: Yanfei Zhou <zyanfei@codeaurora.org>