staging: line6: Split out PODxt Live interfaces

The PODxt Live device has both a POD and a Variax interface.  Add device
type entries for each of these.

Signed-off-by: Chris Rorvick <chris@rorvick.com>
Reviewed-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>