iio: inkern: Remove the 'unused' variable usage in iio_channel_read_max()

The code uses a local variable to initialize a null pointer in order to
avoid accessing this null pointer later on.

Simply removed the 'unused' variable and check for the null pointer just
before accessing it.
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20230623085830.749991-6-herve.codina@bootlin.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/iio/inkern.c

@@ -849,14 +849,10 @@ static int iio_channel_read_max(struct iio_channel *chan,
 				int *val, int *val2, int *type,
 				enum iio_chan_info_enum info)
 {
-	int unused;
 	const int *vals;
 	int length;
 	int ret;
 
-	if (!val2)
-		val2 = &unused;
-
 	ret = iio_channel_read_avail(chan, &vals, type, &length, info);
 	if (ret < 0)
 		return ret;
@@ -869,6 +865,7 @@ static int iio_channel_read_max(struct iio_channel *chan,
 			break;
 		default:
 			*val = vals[4];
+			if (val2)
 				*val2 = vals[5];
 		}
 		return 0;