MFC r210275

MFC r210275

 - Support for Globetrotter iCON 452.
 - Fixed the interface probe routine to only attach to USB interfaces the driver
   actually supports.  This allows other drivers to attach to things like
   MicroSD slots etc.
 - Fixed network interface enumeration to be globally sequential instead of
   relying on the USB interface numbers.  This make sure the first network
   interface always is at uhso0 and the second at usho1 and so on.
 - Added a radio kill switch; exposed through sysctl.
 - Updated the manual page to be verbose about the number of serial ports and
   include iCON 452 in the set of tested hardware.

Submitted by:	Fredrik Lindberg

git-svn-id: svn://svn.freebsd.org/base/stable/8@215478 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f