ice(4): properly use kernel option RSS

Header ice_rss.h uses the kernel RSS interface if option RSS is defined.
However when ice_rss.h is included by ice_lib.h there is no prior
inclusion of ice_opts.h to set RSS causing ifdef RSS to always fail. Add
ice_opts.h to the top of ice_lib.h (like ice_iflib.h) so RSS can be
defined when ice_rss.h is parsed.

With that in place, compilation fails due to a missing defintion of
ICE_DEFAULT_RSS_HASH_CONFIG. It is defined in ice_rss.h only when RSS is
not defined. Since this define is not part of the kernel RSS interface
but ice-specific, it should always be defined. Move its definition
outside of ifdef RSS.

PR: 255309
Reviewed by: mhorne, erj (earlier version)
MFC after: 3 days
Pull Request: https://github.com/freebsd/freebsd-src/pull/1460