netfilter: ipset: deduplicate prefixlen maps

The prefixlen maps used here are identical, and have been since
introduction.  It seems to make sense to use a single large map,
that the preprocessor will fill appropriately.

Signed-off-by: Aaron Conole <[email protected]>
Signed-off-by: Jozsef Kadlecsik <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

Author: apconole