hwmon: (w83627ehf) Fix temp2 source for W83627UHG

Properly set the source of temp2 for the W83627UHG. Also fix a
comment right before that, and document the W83627UHG as reporting up
to 3 temperatures.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>