Staging: iio: Simplify NULL pointer condition

Replace NULL comparrison with its shorter form.
Done with coccinelle:

@replace_rule@
expression e;
@@

-e == NULL
+ !e

Signed-off-by: Cristina Opriceana <cristina.opriceana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/magnetometer/hmc5843_core.c

@@ -579,7 +579,7 @@ int hmc5843_common_probe(struct device *dev, struct regmap *regmap,
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
-	if (indio_dev == NULL)
+	if (!indio_dev)
 		return -ENOMEM;
 
 	dev_set_drvdata(dev, indio_dev);