arm64: dts: mediatek: mt7622: add missing "device_type" to memory nodes

This fixes:
arch/arm64/boot/dts/mediatek/mt7622-rfb1.dtb: /: memory@40000000: 'device_type' is a required property
        from schema $id: http://devicetree.org/schemas/memory.yaml#
arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dtb: /: memory@40000000: 'device_type' is a required property
        from schema $id: http://devicetree.org/schemas/memory.yaml#Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240122132357.31264-1-zajec5@gmail.comSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts

@@ -75,6 +75,7 @@ led-1 {
 
 	memory@40000000 {
 		reg = <0 0x40000000 0 0x40000000>;
+		device_type = "memory";
 	};
 
 	reg_1p8v: regulator-1p8v {

arch/arm64/boot/dts/mediatek/mt7622-rfb1.dts

@@ -57,6 +57,7 @@ key-wps {
 
 	memory@40000000 {
 		reg = <0 0x40000000 0 0x20000000>;
+		device_type = "memory";
 	};
 
 	reg_1p8v: regulator-1p8v {