hwmon: (ad7314) Validate leading zero bits and return error

Leading zero bits are sent on the bus before the temperature value is
transmitted. If any of these bits are high, the connection might be
unstable or there could be no AD7314 / ADT730x (or compatible) at all.
Return -EIO in that case.

Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com>
Fixes: 4f3a6595 ("hwmon: AD7314 driver (ported from IIO)")
Link: https://lore.kernel.org/r/24a50c2981a318580aca8f50d23be7987b69ea00.camel@iris-sensing.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>