dt-bindings: iio: dac: ad5770r: Fix the file path

The following warning is seen with 'make dt_binding_check':

Documentation/devicetree/bindings/iio/dac/adi,ad5770r.yaml: $id: relative path/filename doesn't match actual path or filename

Fix it by removing the "bindings" directory from the file path.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/iio/dac/adi,ad5770r.yaml

@@ -2,7 +2,7 @@
 # Copyright 2020 Analog Devices Inc.
 %YAML 1.2
 ---
-$id: http://devicetree.org/schemas/bindings/iio/dac/adi,ad5770r.yaml#
+$id: http://devicetree.org/schemas/iio/dac/adi,ad5770r.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
 title: Analog Devices AD5770R DAC device driver