[Bluetooth]: Add another ignore parameter to the HCI USB driver

This patchs adds the module parameter ignore_dga to the HCI USB driver
which makes it possible to prevent this driver from being loaded by
some buggy Digianswer devices.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>