Docs: usb: update struct usb_driver

update struct usb_driver from usb-skeleton.c.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/8084ad0e369d4e0bf10598292ee4bac46d09d03d.1635138058.git.philipp.g.hortmann@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>