USB: serial: option: add Quectel UC15, UC20, EC21, and EC25 modems

Add Quectel UC15, UC20, EC21, and EC25.  The EC20 is handled by
qcserial due to a USB VID/PID conflict with an existing Acer
device.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>