feat(stm32mp2-fdts): add memory node

Add ddr node in stm32mp251.dtsi file, which gives addresses to DDR PHY
and DDR controller.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I719bfd1640a8217ff79e79b5b53845b75421d298
diff --git a/fdts/stm32mp251.dtsi b/fdts/stm32mp251.dtsi
index 9e89813..c2c2764 100644
--- a/fdts/stm32mp251.dtsi
+++ b/fdts/stm32mp251.dtsi
@@ -328,6 +328,13 @@
 			reg = <0x44230000 0x10000>;
 		};
 
+		ddr: ddr@48040000 {
+			compatible = "st,stm32mp2-ddr";
+			reg = <0x48040000 0x10000>,
+			      <0x48c00000 0x400000>;
+			status = "okay";
+		};
+
 		pinctrl: pinctrl@44240000 {
 			#address-cells = <1>;
 			#size-cells = <1>;