MFC r231244:

MFC r231244:
- Fix some Xr references:

- - ada(4): ad(4) - removed, ada(4) would be a self-referencing entry
- - cd(4): ad(4) -> ada(4)
- - da(4): ad(4) -> ada(4)
- - DEVICE_PROBE(9):  ugen(5) -> ugen(4)
- - ed(4): dhclinet(8) -> dhclient(8) (typo)
- - lmc(4): Netgraph(4) -> netgraph(4)
- - security(7): rc.conf(8) -> rc.conf(5)
- - sfxge(4): cpuset(8) -> cpuset(1)
- - sbp(4): sysctl(1) -> sysctl(8)
- - portindex(5): build(1) -> build(7)
- - u3g(4): usbconfig(5) -> usbconfig(8)
- - usb_quirk(4): usbconfig(5) -> usbconfig(8)

git-svn-id: svn://svn.freebsd.org/base/stable/9@231718 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f