Make clear in the ipheth(4) hardware notes that this driver is for the
tethering functionality only.  Add a "bugs" section to give a pointer
to usbconfig set_config if the device isn't automatically detected.

MFC after:	3 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272294 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f