ARM: dts: imx6qdl: add enet_out clk support

Like the other i-MX devices the i.MX6 family can output the enet tx
clock on the pad to feed the connected device. Add the missing clk here
to avoid local fixups like: arch/arm/boot/dts/imx6qdl-tx6.dtsi.
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl.dtsi

@@ -1043,8 +1043,9 @@ fec: ethernet@2188000 {
 					     <0 119 IRQ_TYPE_LEVEL_HIGH>;
 				clocks = <&clks IMX6QDL_CLK_ENET>,
 					 <&clks IMX6QDL_CLK_ENET>,
+					 <&clks IMX6QDL_CLK_ENET_REF>,
 					 <&clks IMX6QDL_CLK_ENET_REF>;
-				clock-names = "ipg", "ahb", "ptp";
+				clock-names = "ipg", "ahb", "ptp", "enet_out";
 				fsl,stop-mode = <&gpr 0x34 27>;
 				status = "disabled";
 			};