hwmon: (tmp421) Strengthen detect function

Not all supported chips support the entire I2C address range.
Only accept specific chips at the addresses supported by that chip.
Check for invalid values in conversion rate and status registers.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jean Delvare <jdelvare@suse.de>

Documentation/hwmon/tmp421

@@ -8,11 +8,11 @@ Supported chips:
     Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp421.html
   * Texas Instruments TMP422
     Prefix: 'tmp422'
-    Addresses scanned: I2C 0x2a, 0x4c, 0x4d, 0x4e and 0x4f
+    Addresses scanned: I2C 0x4c, 0x4d, 0x4e and 0x4f
     Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp421.html
   * Texas Instruments TMP423
     Prefix: 'tmp423'
-    Addresses scanned: I2C 0x2a, 0x4c, 0x4d, 0x4e and 0x4f
+    Addresses scanned: I2C 0x4c and 0x4d
     Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp421.html
 
 Authors: