arm64: dts: mt7622: add earlycon to mt7622-rfb1 board

Add earlycon to mt7622-rfb1 as to know what was going on when a certain
fault is happening at the early initialization stage.
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

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

@@ -18,7 +18,7 @@ / {
 	compatible = "mediatek,mt7622-rfb1", "mediatek,mt7622";
 
 	chosen {
-		bootargs = "console=ttyS0,115200n1 swiotlb=512";
+		bootargs = "earlycon=uart8250,mmio32,0x11002000 console=ttyS0,115200n1 swiotlb=512";
 	};
 
 	cpus {