iio: adc: ad-sigma-delta: Allow custom IRQ flags

Before this patch the ad_sigma_delta implementation hardcoded
the irq trigger type to low, assuming that all Sigma-Delta ADCs
have the same interrupt-type.

This patch allows all drivers using the ad_sigma_delta layer to set the
irq trigger type to the one specified in the datasheet.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
diff --git a/drivers/iio/adc/ad7791.c b/drivers/iio/adc/ad7791.c
index 54025ea..abb2393 100644
--- a/drivers/iio/adc/ad7791.c
+++ b/drivers/iio/adc/ad7791.c
@@ -205,6 +205,7 @@ 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,
 };
 
 static int ad7791_read_raw(struct iio_dev *indio_dev,