arm64: dts: mt8183: change rpmsg property name

The the rpmsg property name is changed to "mediatek," to sync with the
vendor name defined in vendor-prefixes.yaml.
Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
Reviewed-By: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20210924033935.2127-7-tinghan.shen@mediatek.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt8183-kukui.dtsi

@@ -813,7 +813,7 @@ &scp {
 
 	cros_ec {
 		compatible = "google,cros-ec-rpmsg";
-		mtk,rpmsg-name = "cros-ec-rpmsg";
+		mediatek,rpmsg-name = "cros-ec-rpmsg";
 	};
 };