Bluetooth: hci_bcm: Add PM for BCM devices

Retrieve "shutdown" and "device_wakeup" GPIOs from ACPI.
Set device off during platform device enumeration.
Set device on only when attached.
As driver can be unbound we need to check if the bcm_device still exists
before calling GPIO's functions, this is protected using device_list_lock.

Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>