iio: humidity: hts221: support active-low interrupts

Add support for active low interrupts (IRQF_TRIGGER_LOW and
IRQF_TRIGGER_FALLING). Configure the device as active high or low
according to the requested irq line.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
diff --git a/drivers/iio/humidity/hts221.h b/drivers/iio/humidity/hts221.h
index 69dfa5c..c3de6e4 100644
--- a/drivers/iio/humidity/hts221.h
+++ b/drivers/iio/humidity/hts221.h
@@ -61,6 +61,7 @@
 extern const struct dev_pm_ops hts221_pm_ops;
 
 int hts221_config_drdy(struct hts221_hw *hw, bool enable);
+int hts221_write_with_mask(struct hts221_hw *hw, u8 addr, u8 mask, u8 val);
 int hts221_probe(struct iio_dev *iio_dev);
 int hts221_set_enable(struct hts221_hw *hw, bool enable);
 int hts221_allocate_buffers(struct hts221_hw *hw);