ASoC: dt-bindings: Drop imx-audio-sgtl5000.txt

The "fsl,imx-audio-sgtl5000" binding is already covered by
fsl-asoc-card.yaml, so remove the old text binding.

Signed-off-by: Rob Herring (Arm) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Acked-by: Conor Dooley <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/sound/imx-audio-sgtl5000.txt

···
-Freescale i.MX audio complex with SGTL5000 codec
-
-Required properties:
-
-  - compatible		: "fsl,imx-audio-sgtl5000"
-
-  - model		: The user-visible name of this sound complex
-
-  - ssi-controller	: The phandle of the i.MX SSI controller
-
-  - audio-codec		: The phandle of the SGTL5000 audio codec
-
-  - audio-routing	: A list of the connections between audio components.
-			  Each entry is a pair of strings, the first being the
-			  connection's sink, the second being the connection's
-			  source. Valid names could be power supplies, SGTL5000
-			  pins, and the jacks on the board:
-
-			  Power supplies:
-			   * Mic Bias
-
-			  SGTL5000 pins:
-			   * MIC_IN
-			   * LINE_IN
-			   * HP_OUT
-			   * LINE_OUT
-
-			  Board connectors:
-			   * Mic Jack
-			   * Line In Jack
-			   * Headphone Jack
-			   * Line Out Jack
-			   * Ext Spk
-
-  - mux-int-port	: The internal port of the i.MX audio muxer (AUDMUX)
-
-  - mux-ext-port	: The external port of the i.MX audio muxer
-
-Note: The AUDMUX port numbering should start at 1, which is consistent with
-hardware manual.
-
-Example:
-
-sound {
-	compatible = "fsl,imx51-babbage-sgtl5000",
-		     "fsl,imx-audio-sgtl5000";
-	model = "imx51-babbage-sgtl5000";
-	ssi-controller = <&ssi1>;
-	audio-codec = <&sgtl5000>;
-	audio-routing =
-		"MIC_IN", "Mic Jack",
-		"Mic Jack", "Mic Bias",
-		"Headphone Jack", "HP_OUT";
-	mux-int-port = <1>;
-	mux-ext-port = <3>;
-};