man: update netconf manual for new attributes

Update this manual to add attributes proxy_neigh and
ignore_routes_with_linkdown.
Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>

man/man8/ip-netconf.8

@@ -15,7 +15,7 @@ The
 .B ip netconf
 utility can monitor IPv4 and IPv6 parameters (see
 .BR "/proc/sys/net/ipv[4|6]/conf/[all|DEV]/" ")"
-like forwarding, rp_filter
+like forwarding, rp_filter, proxy_neigh, ignore_routes_with_linkdown
 or mc_forwarding status.
 
 If no interface is specified, the entry