orinoco_usb: remove version definition

Avoids this:

  CC [M]  drivers/net/wireless/orinoco/orinoco_usb.o
drivers/net/wireless/orinoco/orinoco_usb.c:1759:13: warning: ‘version’ defined but not used

Signed-off-by: John W. Linville <linville@tuxdriver.com>