On a system with both MAX1617 and JC42 sensors, JC42 sensors can be misdetected
as LM84. Strengthen detection sufficiently enough to avoid this misdetection.
Also improve detection for ADM1021.

Modeled after chip detection code in sensors-detect command.

Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Jean Delvare <khali@linux-fr.org>