dt-bindings: iio: imu: st_lsm6dsx: document missing wakeup-source property

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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

@@ -31,6 +31,7 @@ Optional properties:
 - interrupts: interrupt mapping for IRQ. It should be configured with
   flags IRQ_TYPE_LEVEL_HIGH, IRQ_TYPE_EDGE_RISING, IRQ_TYPE_LEVEL_LOW or
   IRQ_TYPE_EDGE_FALLING.
+- wakeup-source: Enables wake up of host system on event.
 
   Refer to interrupt-controller/interrupts.txt for generic interrupt
   client node bindings.