iio: humidity: ens210: remove compiler warning workaround

Rewrite IIO_CHAN_INFO_RAW case to avoid needing to add unreachable code
to work around a compiler warning.

When scoped_guard() was first introduced, compilers could not see when
it returned unconditionally from inside the hidden for loop. This has
since been fixed in the macro definition. So removing the `return
-EINVAL` should be enough. Still, we can improve readability, decrease
indentation and avoid the hidden for loop by rewriting the case without
scoped_guard().

Signed-off-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Author: dlech

drivers/iio/humidity/ens210.c

@@ -149,15 +149,16 @@ static int ens210_read_raw(struct iio_dev *indio_dev,
 	int ret;
 
 	switch (mask) {
-	case IIO_CHAN_INFO_RAW:
-		scoped_guard(mutex, &data->lock) {
-			ret = ens210_get_measurement(
-				indio_dev, channel->type == IIO_TEMP, val);
-			if (ret)
-				return ret;
-			return IIO_VAL_INT;
-		}
-		return -EINVAL; /* compiler warning workaround */
+	case IIO_CHAN_INFO_RAW: {
+		guard(mutex)(&data->lock);
+
+		ret = ens210_get_measurement(indio_dev, channel->type == IIO_TEMP,
+					     val);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT;
+	}
 	case IIO_CHAN_INFO_SCALE:
 		if (channel->type == IIO_TEMP) {
 			*val = 15;