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

This patch refines the DT binding doc for more readability by adding
extra blank lines and indentations.
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/imx-audmux.txt

 Freescale Digital Audio Mux (AUDMUX) device
 
 Required properties:
-- compatible : "fsl,imx21-audmux" for AUDMUX version firstly used on i.MX21,
-  or "fsl,imx31-audmux" for the version firstly used on i.MX31.
-- reg : Should contain AUDMUX registers location and length
+
+  - compatible		: "fsl,imx21-audmux" for AUDMUX version firstly used
+			  on i.MX21, or "fsl,imx31-audmux" for the version
+			  firstly used on i.MX31.
+
+  - reg			: Should contain AUDMUX registers location and length.
 
 An initial configuration can be setup using child nodes.
 
 Required properties of optional child nodes:
-- fsl,audmux-port : Integer of the audmux port that is configured by this
+
+  - fsl,audmux-port	: Integer of the audmux port that is configured by this
 			  child node.
-- fsl,port-config : List of configuration options for the specific port. For
-  imx31-audmux and above, it is a list of tuples <ptcr pdcr>. For
-  imx21-audmux it is a list of pcr values.
+
+  - fsl,port-config	: List of configuration options for the specific port.
+			  For imx31-audmux and above, it is a list of tuples
+			  <ptcr pdcr>. For imx21-audmux it is a list of pcr
+			  values.
 
 Example: