board: sophgo: move ethernet driver to common directory

This will make easier for future boards to reuse the same driver (e.g.
Milk-V Duo 256MB).

Signed-off-by: Hiago De Franco <hfranco@baylibre.com>
Acked-by: Leo Yu-Chi Liang <leo.liang@sifive.com>

board/sophgo/milkv_duo/MAINTAINERS

@@ -2,5 +2,6 @@ Milk-V Duo
 M:	Kongyang Liu <seashell11234455@gmail.com>
 S:	Maintained
 F:	board/sophgo/milkv_duo/
+F:	board/sophgo/common/
 F:	configs/milkv_duo_defconfig
 F:	doc/board/sophgo/milkv_duo.rst

board/sophgo/milkv_duo/Makefile

@@ -3,4 +3,4 @@
 # Copyright (c) 2024, Kongyang Liu <seashell11234455@gmail.com>
 
 obj-y += board.o
-obj-$(CONFIG_NET_LEGACY) += ethernet.o
+obj-$(CONFIG_NET_LEGACY) += ../common/ethernet.o

board/sophgo/milkv_duo/board.c

@@ -5,7 +5,7 @@
 
 #include <dm/lists.h>
 
-#include "ethernet.h"
+#include "../common/ethernet.h"
 
 int board_init(void)
 {