Bluetooth: btusb: Add support for USB based AMP controllers

The Bluetooth HCI transport specification for USB device defines on how
a standard AMP controller is identified and operated. This patch adds
the needed handling to hook it up to the Bluetooth stack.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>