USB: serial: add driver for Suunto ANT+ USB device

This adds a driver for the Suunto ANT+ USB device, exposing it as a usb
serial device.  This lets the userspace "gant" program to talk to the
device to communicate over the ANT+ protocol to any devices it finds.

Reported-by: Steinar Gunderson <sgunderson@bigfoot.com>
Tested-by: Steinar Gunderson <sgunderson@bigfoot.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>