Reduce usage of netif/ethernet.h header, mostly lwip/prot/ethernet.h is sufficient

src/core/ipv4/etharp.c

@@ -52,6 +52,7 @@
 #include "lwip/snmp.h"
 #include "lwip/dhcp.h"
 #include "lwip/autoip.h"
+#include "netif/ethernet.h"
 
 #include <string.h>
 

src/core/ipv6/ethip6.c

@@ -51,7 +51,7 @@
 #include "lwip/inet_chksum.h"
 #include "lwip/netif.h"
 #include "lwip/icmp6.h"
-#include "netif/ethernet.h"
+#include "lwip/prot/ethernet.h"
 
 #include <string.h>
 

src/core/netif.c

@@ -58,6 +58,8 @@
 #endif /* LWIP_NETIF_LOOPBACK_MULTITHREADING */
 #endif /* ENABLE_LOOPBACK */
 
+#include "netif/ethernet.h"
+
 #if LWIP_AUTOIP
 #include "lwip/autoip.h"
 #endif /* LWIP_AUTOIP */