riscv: dts: sifive: Add ethernet0 to the aliases node

U-Boot expects this alias to be in place in order to fix up the mac
address of the ethernet node.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/boot/dts/sifive/fu540-c000.dtsi

@@ -13,6 +13,7 @@ / {
 	aliases {
 		serial0 = &uart0;
 		serial1 = &uart1;
+		ethernet0 = &eth0;
 	};
 
 	chosen {