USB: serial: option: add support for Quectel UC20

Add support for Quectel UC20 and blacklist the QMI interface.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Cc: stable <stable@vger.kernel.org>
[johan: amend commit message ]
Signed-off-by: Johan Hovold <johan@kernel.org>