ARM: dts: imx6ul-14x14-evk: Pass "fsl, sai-mclk-direction-output"

Pass "fsl,sai-mclk-direction-output" to the sai2 node, so that the
SAI2_MCLK can be an output.
Signed-off-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6ul-14x14-evk.dts

@@ -146,6 +146,7 @@
 			  <&clks IMX6UL_CLK_SAI2>;
 	assigned-clock-parents = <&clks IMX6UL_CLK_PLL4_AUDIO_DIV>;
 	assigned-clock-rates = <0>, <12288000>;
+	fsl,sai-mclk-direction-output;
 	status = "okay";
 };