USB: usb.h: fix kernel-doc notation

Fix usb.h kernel-doc warnings:

Warning(include/linux/usb.h:918): Excess struct/union/enum/typedef member 'nodename' description in 'usb_device_driver'
Warning(include/linux/usb.h:939): No description found for parameter 'nodename'
Warning(include/linux/usb.h:1219): No description found for parameter 'sg'
Warning(include/linux/usb.h:1219): No description found for parameter 'num_sgs'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>