Bluetooth: hci_qca: Add poweroff support during hci down for wcn3990

This patch enables power off support for hci down and power on support
for hci up. As wcn3990 power sources are ignited by regulators, we will
turn off them during hci down, i.e. an complete power off of wcn3990.
So while hci up, will call vendor setup which will turn on the regulators,
requests BT chip version and download the firmware.

Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>