dts: dm: fec: imx53: Provide proper compatible string for imx53 fec driver

After this change the DM FEC ETH driver can be also reused on some imx53
devices.

Signed-off-by: Lukasz Majewski <lukma@denx.de>

drivers/net/fec_mxc.c

@@ -1345,6 +1345,7 @@ static const struct udevice_id fecmxc_ids[] = {
 	{ .compatible = "fsl,imx6sl-fec" },
 	{ .compatible = "fsl,imx6sx-fec" },
 	{ .compatible = "fsl,imx6ul-fec" },
+	{ .compatible = "fsl,imx53-fec" },
 	{ }
 };