arm64: dts: renesas: spider-cpu: Add missing bootargs

This patch adds missing bootargs for R-Car S4 Spider board.

One note is that current Spider board doesn't have Ethernet
support yet, but this patch adds standard settings for it, too.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87leqo58ox.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm64/boot/dts/renesas/r8a779f0-spider-cpu.dtsi

@@ -17,6 +17,7 @@ aliases {
 	};
 
 	chosen {
+		bootargs = "ignore_loglevel rw root=/dev/nfs ip=on";
 		stdout-path = "serial0:115200n8";
 	};