USB: serial: qcserial: add Dell DW5818, DW5819

Dell Wireless 5819/5818 devices are re-branded Sierra Wireless MC74
series which will by default boot with vid 0x413c and pid's 0x81cf,
0x81d0, 0x81d1, 0x81d2.

Signed-off-by: Shrirang Bagul <shrirang.bagul@canonical.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>