net: ethernet: Enhance debug prints by printing ifindex

Network interface index number is useful to see in
debug messages so print it.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

subsys/net/l2/ethernet/ethernet.c

@@ -87,10 +87,11 @@ void net_eth_ipv6_mcast_to_mac_addr(const struct in6_addr *ipv6_addr,
 			 net_sprint_ll_addr((src)->addr,		   \
 					    sizeof(struct net_eth_addr))); \
 									   \
-		NET_DBG("iface %p src %s dst %s type 0x%x len %zu",	   \
-			net_pkt_iface(pkt), out,		   \
-			net_sprint_ll_addr((dst)->addr,	   \
-					    sizeof(struct net_eth_addr)), \
+		NET_DBG("iface %d (%p) src %s dst %s type 0x%x len %zu",   \
+			net_if_get_by_iface(net_pkt_iface(pkt)),	   \
+			net_pkt_iface(pkt), out,			   \
+			net_sprint_ll_addr((dst)->addr,			   \
+					    sizeof(struct net_eth_addr)),  \
 			type, (size_t)len);				   \
 	}
 
@@ -103,10 +104,11 @@ void net_eth_ipv6_mcast_to_mac_addr(const struct in6_addr *ipv6_addr,
 			 net_sprint_ll_addr((src)->addr,		   \
 					    sizeof(struct net_eth_addr))); \
 									   \
-		NET_DBG("iface %p src %s dst %s type 0x%x "		   \
+		NET_DBG("iface %d (%p) src %s dst %s type 0x%x "	   \
 			"tag %d %spri %d len %zu",			   \
-			net_pkt_iface(pkt), out,		   \
-			net_sprint_ll_addr((dst)->addr,	   \
+			net_if_get_by_iface(net_pkt_iface(pkt)),	   \
+			net_pkt_iface(pkt), out,			   \
+			net_sprint_ll_addr((dst)->addr,			   \
 				   sizeof(struct net_eth_addr)),	   \
 			type, net_eth_vlan_get_vid(tci),		   \
 			tagstrip ? "(stripped) " : "",			   \