hwmon: (lm90) Make SA56004 detection more robust

With a device ID register value of 0, the SA56004 detection is rather
weak. Check several other register too to confirm the detection, as we
do for other supported devices.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Stijn Devriendt <sdevrien@cisco.com>
Cc: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Stijn Devriendt <sdevrien@cisco.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>