iio: lp8788_adc: fix a parent device in _probe()

 The lp8788-adc is a platform driver of lp8788-mfd.
 The platform device is allocated when mfd_add_devices() is called
 in lp8788-mfd.
 On the other hand, 'lp->dev' is the i2c client device.

 Therefore, this 'platform_device' is a proper parent device of
 iio device and device kernel message.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/lp8788_adc.c

@@ -214,7 +214,7 @@ static int __devinit lp8788_adc_probe(struct platform_device *pdev)
 
 	mutex_init(&adc->lock);
 
-	indio_dev->dev.parent = lp->dev;
+	indio_dev->dev.parent = &pdev->dev;
 	indio_dev->name = pdev->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &lp8788_adc_info;
@@ -223,7 +223,7 @@ static int __devinit lp8788_adc_probe(struct platform_device *pdev)
 
 	ret = iio_device_register(indio_dev);
 	if (ret) {
-		dev_err(lp->dev, "iio dev register err: %d\n", ret);
+		dev_err(&pdev->dev, "iio dev register err: %d\n", ret);
 		goto err_iio_device;
 	}