HID: wacom: Enable HID_GENERIC codepath for Bluetooth devices

There no reason a Bluetooth device with the appropriate HID descriptor couldn't
be used through the HID_GENERIC codepath in the future. Ensure that the driver
attempts to bind to these devices.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>