ARM: dts: marzen: Add rw to bootargs and use ip=dhcp

Add rw as bootargs parameter and change from ip=on to ip=dhcp to make the
Marzen board bootargs match other boards from Renesas. No need to be special.
Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7779-marzen.dts

@@ -21,7 +21,7 @@ aliases {
 	};
 
 	chosen {
-		bootargs = "ignore_loglevel root=/dev/nfs ip=on";
+		bootargs = "ignore_loglevel rw root=/dev/nfs ip=dhcp";
 		stdout-path = "serial0:115200n8";
 	};