rt2x00: Add unknown Toshiba device

Add unknown Toshiba device, mentioned in rt3572sta sources, under
CONFIG_RT2800USB_UNKNOWN

Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>