net: increase frag hash size

Increase fragmentation hash bucket size to 1024 from old 64 elems.

After we increased the frag mem limits commit c2a93660 (net: increase
fragment memory usage limits) the hash size of 64 elements is simply
too small.  Also considering the mem limit is per netns and the hash
table is shared for all netns.

For the embedded people, note that this increase will change the hash
table/array from using approx 1 Kbytes to 16 Kbytes.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>