bits.

The motivation here is to eventually teach netisr and potentially
other networking subsystems a bit more about how RSS work queues / buckets
are configured so things have a hope of auto-configuring in the future.

* net/rss_config.[ch] takes care of the generic bits for doing
  configuration, hash function selection, etc;
* topelitz.[ch] is now in net/ rather than netinet/;
* (and would be in libkern if it didn't directly include RSS_KEYSIZE;
  that's a later thing to fix up.)
* netinet/in_rss.[ch] now just contains the IPv4 specific methods;
* and netinet/in6_rss.[ch] now just contains the IPv6 specific methods.

This should have no functional impact on anyone currently using
the RSS support.

Differential Revision:	D1383
Reviewed by:	gnn, jfv (intel driver bits)