iio: st_sensors: Init trigger before irq request

This fixes a possible race where an interrupt arrives before complete
initialization and crashes because iio_trigger_get_drvdata returns NULL.

Cc: Giuseppe Barba <giuseppe.barba@st.com>
Cc: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Crestez Dan Leonard <leonard.crestez@intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/common/st_sensors/st_sensors_trigger.c

@@ -97,6 +97,10 @@ int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
 		return -ENOMEM;
 	}
 
+	iio_trigger_set_drvdata(sdata->trig, indio_dev);
+	sdata->trig->ops = trigger_ops;
+	sdata->trig->dev.parent = sdata->dev;
+
 	irq = sdata->get_irq_data_ready(indio_dev);
 	irq_trig = irqd_get_trigger_type(irq_get_irq_data(irq));
 	/*
@@ -158,10 +162,6 @@ int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
 		goto iio_trigger_free;
 	}
 
-	iio_trigger_set_drvdata(sdata->trig, indio_dev);
-	sdata->trig->ops = trigger_ops;
-	sdata->trig->dev.parent = sdata->dev;
-
 	err = iio_trigger_register(sdata->trig);
 	if (err < 0) {
 		dev_err(&indio_dev->dev, "failed to register iio trigger.\n");