net/neigh: Extend dump filter to proxy neighbor dumps

Move the attribute parsing from neigh_dump_table to neigh_dump_info, and
pass the filter arguments down to neigh_dump_table in a new struct. Add
the filter option to proxy neigh dumps as well to make them consistent.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>