Bluetooth: Use BTUSB_BROKEN_ISOC flag for CSR USB sniffer devices

Instead of setting data->isoc manually, use BTUSB_BROKEN_ISOC to
indicate that isochronous endpoints are not needed for CSR USB
sniffer devices.

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