dt-bindings: iio: dac: ad5791: ldac gpio is active low

On the example, the ldac gpio is flagged as active high, when in reality
its an active low gpio. Fix the example by using the active low flag for
the ldac gpio.

Fixes: baaa92d2 ("dt-bindings: iio: dac: ad5791: Add optional reset, clr and ldac gpios")
Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20241106103824.579292-1-ahaslam@baylibre.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>