iio: st_sensors: handle memory allocation failure to fix null pointer dereference

A null pointer deference on pdata can occur if the allocation of
pdata fails.  Fix this by adding a null pointer check and handle
the -ENOMEM failure in the caller.

Addresses-Coverity: ("Dereference null return value")
Fixes: 3ce85cc4 ("iio: st_sensors: get platform data from device tree")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/common/st_sensors/st_sensors_core.c

@@ -328,6 +328,8 @@ static struct st_sensors_platform_data *st_sensors_dev_probe(struct device *dev,
 		return NULL;
 
 	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return ERR_PTR(-ENOMEM);
 	if (!device_property_read_u32(dev, "st,drdy-int-pin", &val) && (val <= 2))
 		pdata->drdy_int_pin = (u8) val;
 	else
@@ -371,6 +373,8 @@ int st_sensors_init_sensor(struct iio_dev *indio_dev,
 
 	/* If OF/DT pdata exists, it will take precedence of anything else */
 	of_pdata = st_sensors_dev_probe(indio_dev->dev.parent, pdata);
+	if (IS_ERR(of_pdata))
+		return PTR_ERR(of_pdata);
 	if (of_pdata)
 		pdata = of_pdata;