iio: mxs-lradc: Fix misuse of iio->trig

The struct iio_dev .trig field is to be used only by the IIO core,
the driver shall not fill this field. This fixes ugly crash when
the driver is compiled as a module and the module is rmmod'd.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/mxs-lradc.c

@@ -661,12 +661,13 @@ static int mxs_lradc_trigger_init(struct iio_dev *iio)
 {
 	int ret;
 	struct iio_trigger *trig;
+	struct mxs_lradc *lradc = iio_priv(iio);
 
 	trig = iio_trigger_alloc("%s-dev%i", iio->name, iio->id);
 	if (trig == NULL)
 		return -ENOMEM;
 
-	trig->dev.parent = iio->dev.parent;
+	trig->dev.parent = lradc->dev;
 	iio_trigger_set_drvdata(trig, iio);
 	trig->ops = &mxs_lradc_trigger_ops;
 
@@ -676,15 +677,17 @@ static int mxs_lradc_trigger_init(struct iio_dev *iio)
 		return ret;
 	}
 
-	iio->trig = trig;
+	lradc->trig = trig;
 
 	return 0;
 }
 
 static void mxs_lradc_trigger_remove(struct iio_dev *iio)
 {
-	iio_trigger_unregister(iio->trig);
-	iio_trigger_free(iio->trig);
+	struct mxs_lradc *lradc = iio_priv(iio);
+
+	iio_trigger_unregister(lradc->trig);
+	iio_trigger_free(lradc->trig);
 }
 
 static int mxs_lradc_buffer_preenable(struct iio_dev *iio)