USB: cdc-wdm: remove unneeded DRIVER_VERSION define

No one uses the DRIVER_VERSION define in this driver, so just delete it.

Cc: Oliver Neukum <oneukum@suse.com>
Cc: "Bjørn Mork" <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>