ARM: dts: imx7s-warp: Let the codec control MCLK pinctrl

sgtl5000 codec needs MCLK clock to be provided so that it can
successfully read/write via I2C, so we should better let the
codec control the pinctrl for such pin.

Thanks to Stefan Agner who provided the fix on Toradex's tree:
http://git.toradex.com/cgit/linux-toradex.git/commit/?h=toradex_imx_4.1.15_1.0.0_ga-next&id=0a55a7e5f58d46eef0d4d1d357d89e36d0c32fa4Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx7s-warp.dts

@@ -199,6 +199,8 @@ codec: sgtl5000@0a {
 		reg = <0x0a>;
 		compatible = "fsl,sgtl5000";
 		clocks = <&clks IMX7D_AUDIO_MCLK_ROOT_CLK>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_sai1_mclk>;
 		VDDA-supply = <&vgen4_reg>;
 		VDDIO-supply = <&vgen4_reg>;
 		VDDD-supply = <&vgen2_reg>;
@@ -291,7 +293,12 @@ MX7D_PAD_SAI1_RX_DATA__SAI1_RX_DATA0	0x1f
 			MX7D_PAD_SAI1_TX_BCLK__SAI1_TX_BCLK	0x1f
 			MX7D_PAD_SAI1_TX_SYNC__SAI1_TX_SYNC	0x1f
 			MX7D_PAD_SAI1_TX_DATA__SAI1_TX_DATA0	0x30
-			MX7D_PAD_SAI1_MCLK__SAI1_MCLK		0x1f
+		>;
+	};
+
+	pinctrl_sai1_mclk: sai1mclkgrp {
+		fsl,pins = <
+			MX7D_PAD_SAI1_MCLK__SAI1_MCLK           0x1f
 		>;
 	};