ARM: dts: imx7ulp: add mmdc support

i.MX7ULP has a MMDC module to control DDR, it reuses
i.MX6Q's MMDC module, add support for it.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx7ulp.dtsi

@@ -286,6 +286,12 @@ lpuart7: serial@40a70000 {
 			status = "disabled";
 		};
 
+		memory-controller@40ab0000 {
+			compatible = "fsl,imx7ulp-mmdc", "fsl,imx6q-mmdc";
+			reg = <0x40ab0000 0x1000>;
+			clocks = <&pcc3 IMX7ULP_CLK_MMDC>;
+		};
+
 		iomuxc1: pinctrl@40ac0000 {
 			compatible = "fsl,imx7ulp-iomuxc1";
 			reg = <0x40ac0000 0x1000>;