Add sysctl knob to disable port power on a specific USB HUB. You need
to reset the USB HUB using "usbconfig -d X.Y reset" or boot having the
setting in /boot/loader.conf before it activates.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272822 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f