Fix trivial kernel-doc warnings:
Warning(include/linux/usb.h:574): No description found for parameter 'usb3_lpm_enabled'
Warning(include/linux/usb.h:574): Excess struct/union/enum/typedef member 'usb_classdev' description in 'usb_device'
Warning(include/linux/usb.h:574): Excess struct/union/enum/typedef member 'usbfs_dentry' description in 'usb_device'