usb: cdc_acm: Add quirk for Castles VEGA3000

The device (a POS terminal) implements CDC ACM, but has not union
descriptor.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Oliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>