ASoC: imx-spdif: Add indentation for binding doc to increase readability

This patch simply adds indentations for DT binding doc to increase readability
without changing any contents.
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/imx-audio-spdif.txt

@@ -11,14 +11,16 @@ Required properties:
 
 Optional properties:
 
-  - spdif-out : This is a boolean property. If present, the transmitting
-    function of S/PDIF will be enabled, indicating there's a physical
-    S/PDIF out connector/jack on the board or it's connecting to some
-    other IP block, such as an HDMI encoder/display-controller.
+  - spdif-out		: This is a boolean property. If present, the
+			  transmitting function of S/PDIF will be enabled,
+			  indicating there's a physical S/PDIF out connector
+			  or jack on the board or it's connecting to some
+			  other IP block, such as an HDMI encoder or
+			  display-controller.
 
   - spdif-in		: This is a boolean property. If present, the receiving
-    function of S/PDIF will be enabled, indicating there's a physical
-    S/PDIF in connector/jack on the board.
+			  function of S/PDIF will be enabled, indicating there
+			  is a physical S/PDIF in connector/jack on the board.
 
 * Note: At least one of these two properties should be set in the DT binding.