Staging: line6: use module_usb_driver()

Now that our module_init/exit path is just registering and unregistering
the usb driver, we can use module_usb_driver() instead.  This also has
the nice side affect of removing the unneeded printk for the module
version number.

CC: Markus Grabner <grabner@icg.tugraz.at>
CC: Stefan Hajnoczi <stefanha@gmail.com>
CC: Julia Lawall <julia@diku.dk>
CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>