ARM: dts: stm32: fix memory nodes to match with DT validation tool

DT validation ("make dtbs_check") has shown that some memory nodes were not
correctly written. This commit fixes this kind of issue:

"stm32f746-disco.dt.yaml: /: memory: False schema does not allow
{'device_type': ['memory'], 'reg': [[3221225472, 8388608]]}"

Signed-off-by: Alexandre Torgue <[e-mail]>

arch/arm/boot/dts/stm32429i-eval.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@00000000 {
 		device_type = "memory";
 		reg = <0x00000000 0x2000000>;
 	};

arch/arm/boot/dts/stm32746g-eval.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@c0000000 {
 		device_type = "memory";
 		reg = <0xc0000000 0x2000000>;
 	};

arch/arm/boot/dts/stm32f429-disco.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@90000000 {
 		device_type = "memory";
 		reg = <0x90000000 0x800000>;
 	};

arch/arm/boot/dts/stm32f469-disco.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@00000000 {
 		device_type = "memory";
 		reg = <0x00000000 0x1000000>;
 	};

arch/arm/boot/dts/stm32f746-disco.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@c0000000 {
 		device_type = "memory";
 		reg = <0xC0000000 0x800000>;
 	};

arch/arm/boot/dts/stm32f769-disco.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@c0000000 {
 		device_type = "memory";
 		reg = <0xC0000000 0x1000000>;
 	};

arch/arm/boot/dts/stm32h743i-disco.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@d0000000 {
 		device_type = "memory";
 		reg = <0xd0000000 0x2000000>;
 	};

arch/arm/boot/dts/stm32h743i-eval.dts

···
 		stdout-path = "serial0:115200n8";
 	};
 
-	memory {
+	memory@d0000000 {
 		device_type = "memory";
 		reg = <0xd0000000 0x2000000>;
 	};

arch/arm/boot/dts/stm32mp157a-dk1.dts

···
 	};
 
 	memory@c0000000 {
+		device_type = "memory";
 		reg = <0xc0000000 0x20000000>;
 	};