Documentation: dt: iio: imu: st_lsm6dsx: add st,drdy-int-pin property

Add st,drdy-int-pin property to select interrupt pin of the package
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi@st.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/imu/st_lsm6dsx.txt

@@ -7,6 +7,8 @@ Required properties:
 - reg: i2c address of the sensor / spi cs line
 
 Optional properties:
+- st,drdy-int-pin: the pin on the package that will be used to signal
+  "data ready" (valid values: 1 or 2).
 - interrupt-parent: should be the phandle for the interrupt controller
 - interrupts: interrupt mapping for IRQ. It should be configured with
   flags IRQ_TYPE_LEVEL_HIGH or IRQ_TYPE_EDGE_RISING.