iio: adc: ad7791: fix IRQ flags

The interrupt is triggered on the falling edge rather than being a level
low interrupt.

Fixes: da4d3d6b ("iio: adc: ad-sigma-delta: Allow custom IRQ flags")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20230120124645.819910-1-nuno.sa@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7791.c

@@ -253,7 +253,7 @@ static const struct ad_sigma_delta_info ad7791_sigma_delta_info = {
 	.has_registers = true,
 	.addr_shift = 4,
 	.read_mask = BIT(3),
-	.irq_flags = IRQF_TRIGGER_LOW,
+	.irq_flags = IRQF_TRIGGER_FALLING,
 };
 
 static int ad7791_read_raw(struct iio_dev *indio_dev,