iproute2: add vcan to ip link help text

Hello Stephen,

thanks für the commit of my last CAN patch.

Today i got a hint, that the help text of 'ip link' can be improved also.

Many thanks!

Oliver
Signed-Off-By: Oliver Hartkopp <oliver@hartkopp.net>

ip/iplink.c

@@ -72,7 +72,7 @@ void iplink_usage(void)
 
 	if (iplink_have_newlink()) {
 		fprintf(stderr, "\n");
-		fprintf(stderr, "TYPE := { vlan | veth | dummy | ifb | macvlan }\n");
+		fprintf(stderr, "TYPE := { vlan | veth | vcan | dummy | ifb | macvlan }\n");
 	}
 	exit(-1);
 }