BugLink: http://bugs.launchpad.net/bugs/1768825

commit fe710508 upstream.

Add simple driver for libtransistor USB console.
This device is implemented in software:
https://github.com/reswitched/libtransistor/blob/development/lib/usb_serial.cSigned-off-by: Collin May <collin@collinswebsite.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>