USB: convert usb.h struct usb_device to kernel-doc

Convert struct usb_device to use kernel-doc notation.
Please especially check the @filelist and @usb_classdev descriptions.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>