[Bluetooth] Make use of device_move() for RFCOMM TTY devices

In the case of bound RFCOMM TTY devices the parent is not available
before its usage. So when opening a RFCOMM TTY device, move it to
the corresponding ACL device as a child. When closing the device,
move it back to the virtual device tree.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>