Staging: iio: impedance-analyzer: Remove explicit NULL comparison

This patch removes explicit NULL comparison and replaces it with
its shorter form. Detected with coccinelle.
Signed-off-by: Cristina Opriceana <cristina.opriceana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/impedance-analyzer/ad5933.c

@@ -703,7 +703,7 @@ static int ad5933_probe(struct i2c_client *client,
 	struct iio_dev *indio_dev;
 
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*st));
-	if (indio_dev == NULL)
+	if (!indio_dev)
 		return -ENOMEM;
 
 	st = iio_priv(indio_dev);