sfxge(4): support more RSS hash configurations

Modern firmwares on EF10 adapters have support for
more traffic classes eligible for hash computation.
Also, it has become possible to adjust hashing per
individual class and select distinct packet fields
which will be able to contribute to the hash value.

This patch adds support for the mentioned features.

Submitted by: Ivan Malov <ivan.malov at oktetlabs.ru>
Sponsored by: Solarflare Communications, Inc.
Differential Revision: https://reviews.freebsd.org/D18231