ll_types: add netlink ARPHRD

This adds ARPHRD_NETLINK to ll_types so that it can be properly
shown e.g. in `ip a`:

 8: nlmon: <NOARP,UP,LOWER_UP> mtu 3776 qdisc noqueue state UNKNOWN group default
    link/netlink
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

lib/ll_types.c

@@ -104,6 +104,7 @@ __PF(PHONET, phonet)
 __PF(PHONET_PIPE, phonet_pipe)
 __PF(CAIF, caif)
 __PF(IP6GRE, gre6)
+__PF(NETLINK, netlink)
 
 __PF(NONE, none)
 __PF(VOID,void)