USB: serial: cp210x: add ID for IMST iM871A-USB

The device IMST USB-Stick for Smart Meter is a rebranded IMST iM871A-USB
Wireless M-Bus USB-adapter. It is used to read wireless water, gas and
electricity meters.

Signed-off-by: Leonard Dallmayr <leonard.dallmayr@mailbox.org>
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>