mips: dts: lantiq: danube: add missing burst length property

The upstream dts lacks the lantiq,{rx/tx}-burst-length property. Other
issues were also fixed:
arch/mips/boot/dts/lantiq/danube_easy50712.dtb: etop@e180000 (lantiq,etop-xway): 'interrupt-names' is a required property
	from schema $id: http://devicetree.org/schemas/net/lantiq,etop-xway.yaml#
arch/mips/boot/dts/lantiq/danube_easy50712.dtb: etop@e180000 (lantiq,etop-xway): 'lantiq,tx-burst-length' is a required property
	from schema $id: http://devicetree.org/schemas/net/lantiq,etop-xway.yaml#
arch/mips/boot/dts/lantiq/danube_easy50712.dtb: etop@e180000 (lantiq,etop-xway): 'lantiq,rx-burst-length' is a required property
	from schema $id: http://devicetree.org/schemas/net/lantiq,etop-xway.yaml#

Fixes: 14d4e30 ("net: lantiq: configure the burst length in ethernet drivers")
Signed-off-by: Aleksander Jan Bajkowski <[email protected]>
Acked-by: Jakub Kicinski <[email protected]>

Author: abajk

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

@@ -87,8 +87,11 @@
 			reg = <0xe180000 0x40000>;
 			interrupt-parent = <&icu0>;
 			interrupts = <73 78>;
+			interrupt-names = "tx", "rx";
 			phy-mode = "rmii";
 			mac-address = [ 00 11 22 33 44 55 ];
+			lantiq,rx-burst-length = <4>;
+			lantiq,tx-burst-length = <4>;
 		};
 
 		stp0: stp@e100bb0 {