ARM: shmobile: Include all 2 GiB of memory on APE6EVM DT Ref

Add 1GiB of DRAM at 0x2_0000_0000 to support the full 2GiB
of APE6EVM system memory also in case of DT reference.
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a73a4-ape6evm-reference.dts

@@ -25,6 +25,11 @@ memory@40000000 {
 		reg = <0 0x40000000 0 0x40000000>;
 	};
 
+	memory@200000000 {
+		device_type = "memory";
+		reg = <2 0x00000000 0 0x40000000>;
+	};
+
 	vcc_mmc0: regulator@0 {
 		compatible = "regulator-fixed";
 		regulator-name = "MMC0 Vcc";