dpif-netdev: Use cmap instead of hmap.

This requires less locking and makes introducing lockless classifier
lookups possible.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
lib/hash: Abstract hash interface.

Use generic names hash_add() and hash_finish() instead of mhash_*
equivalents.  This makes future changes to hash implentations more
localized.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>