iio: st_sensors: decouple irq1 configuration parameters from the irq2 ones

Separate data-ready configuration parameters for INT1 and INT2 pins in
st_sensor_data_ready_irq data structure. That change will be use to
properly support LIS2DW12 accel sensor.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>