riscv: sifive_u: 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.

This is to keep in sync with Linux kernel commit below:
https://patchwork.kernel.org/patch/11133033/Signed-off-by: NBin Meng <bmeng.cn@gmail.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

hw/riscv/sifive_u.c

@@ -270,6 +270,10 @@ static void create_fdt(SiFiveUState *s, const struct MemmapEntry *memmap,
         s->soc.gem.conf.macaddr.a, ETH_ALEN);
     qemu_fdt_setprop_cell(fdt, nodename, "#address-cells", 1);
     qemu_fdt_setprop_cell(fdt, nodename, "#size-cells", 0);
+
+    qemu_fdt_add_subnode(fdt, "/aliases");
+    qemu_fdt_setprop_string(fdt, "/aliases", "ethernet0", nodename);
+
     g_free(nodename);
 
     nodename = g_strdup_printf("/soc/ethernet@%lx/ethernet-phy@0",
@@ -297,7 +301,6 @@ static void create_fdt(SiFiveUState *s, const struct MemmapEntry *memmap,
         qemu_fdt_setprop_string(fdt, "/chosen", "bootargs", cmdline);
     }
 
-    qemu_fdt_add_subnode(fdt, "/aliases");
     qemu_fdt_setprop_string(fdt, "/aliases", "serial0", nodename);
 
     g_free(nodename);