ARM: dts: stm32mp1: correct ddr node

This patch fix the warning:
dt.dts: Warning (simple_bus_reg): Node /soc/ddr@5A003000
simple-bus unit address format error, expected "5a003000"

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>

arch/arm/dts/stm32mp15-ddr.dtsi

@@ -5,7 +5,7 @@
 
 / {
 	soc {
-		ddr: ddr@5A003000 {
+		ddr: ddr@5a003000 {
 			u-boot,dm-pre-reloc;
 
 			compatible = "st,stm32mp1-ddr";