Revert "rtnetlink: return EINVAL when request cannot succeed"

This reverts commit b6177d3240a4

ip-link command is testing kernel capability by sending a RTM_NEWLINK
request, without any argument. It accepts everything in reply, except
EOPNOTSUPP and EINVAL (functions iplink_have_newlink / accept_msg)

So we must keep compatiblity here, invalid empty message should not
return EINVAL

Signed-off-by: Florent Fourcot <[e-mail]>
Tested-by: Guillaume Nault <[e-mail]>
Reviewed-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/rtnetlink.c

···
 			return rtnl_group_changelink(skb, net,
 						nla_get_u32(tb[IFLA_GROUP]),
 						ifm, extack, tb);
-		return -EINVAL;
+		return -ENODEV;
 	}
 
 	if (tb[IFLA_MAP] || tb[IFLA_PROTINFO])