mips: lantiq: danube: add model to EASY50712 dts

This fixes the following warning:
arch/mips/boot/dts/lantiq/danube_easy50712.dtb: / (lantiq,xway): 'model' is a required property
	from schema $id: http://devicetree.org/schemas/root-node.yaml#

Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: abajk

arch/mips/boot/dts/lantiq/danube_easy50712.dts

@@ -4,6 +4,8 @@
 /include/ "danube.dtsi"
 
 / {
+	model = "Intel EASY50712";
+
 	chosen {
 		bootargs = "console=ttyLTQ0,115200 init=/etc/preinit";
 	};