Create a driver to support the hardware monitoring chip present in
the Zyxel NSA320 and some of the other Zyxel NAS devices.

The driver reads fan speed and temperature from a suitably
pre-programmed MCU on the device.
Signed-off-by: NAdam Baker <linux@baker-net.org.uk>
[groeck: Dropped .owner field initialization]
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>