usb: qcserial: remove interface number matching

Matching on interface numbers was not such a good idea
for multi-function serial devices after all. It is much
better do create well defined device layouts, allowing
a single match entry per device.

Remove this now unused code.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>