USB: serial: ftdi_sio: add Id for Physik Instrumente E-870

This adds support for the Physik Instrumente E-870 PIShift Drive
Electronics, a Piezo motor driver.

Signed-off-by: Martin Teichmann <martin.teichmann@xfel.eu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>