iio: chemical: sunrise_co2: set val parameter only on success

Clang static analysis reports this representative warning

sunrise_co2.c:410:9: warning: Assigned value is garbage or undefined
  *val = value;
       ^ ~~~~~

The ealier call to sunrise_read_word can fail without setting
value.  So defer setting val until we know the read was successful.

Fixes: c397894e ("iio: chemical: Add Senseair Sunrise 006-0-007 driver")
Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20211224150833.3278236-1-trix@redhat.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/chemical/sunrise_co2.c

@@ -407,24 +407,24 @@ static int sunrise_read_raw(struct iio_dev *iio_dev,
 			mutex_lock(&sunrise->lock);
 			ret = sunrise_read_word(sunrise, SUNRISE_CO2_FILTERED_COMP_REG,
 						&value);
-			*val = value;
 			mutex_unlock(&sunrise->lock);
 
 			if (ret)
 				return ret;
 
+			*val = value;
 			return IIO_VAL_INT;
 
 		case IIO_TEMP:
 			mutex_lock(&sunrise->lock);
 			ret = sunrise_read_word(sunrise, SUNRISE_CHIP_TEMPERATURE_REG,
 						&value);
-			*val = value;
 			mutex_unlock(&sunrise->lock);
 
 			if (ret)
 				return ret;
 
+			*val = value;
 			return IIO_VAL_INT;
 
 		default: