arm64: dts: imx8qxp: add "fsl,imx8qm-fec" compatible string for FEC

Add "fsl,imx8qm-fec" compatible string for FEC to support new feature
(RGMII delayed clock).
Signed-off-by: NJoakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/arm64/boot/dts/freescale/imx8qxp-ss-conn.dtsi

@@ -17,9 +17,9 @@
 };
 
 &fec1 {
-	compatible = "fsl,imx8qxp-fec", "fsl,imx6sx-fec";
+	compatible = "fsl,imx8qxp-fec", "fsl,imx8qm-fec", "fsl,imx6sx-fec";
 };
 
 &fec2 {
-	compatible = "fsl,imx8qxp-fec", "fsl,imx6sx-fec";
+	compatible = "fsl,imx8qxp-fec", "fsl,imx8qm-fec", "fsl,imx6sx-fec";
 };