Expose full 32bit RSS hash from card regardless of whether RSS is defined or
not. When doing multiqueue, we are all setup to have full 32bit RSS hash from
the card. We do not need to hide that under "ifdef RSS" and should expose that
by default so others like lagg(4) can use that and avoid hashing the traffic by
themselves.

While here, delete the FreeBSD version check and use of deprecated M_FLOWID.

Reviewed by: adrian, erj
MFC after: 1 week
Sponsored by: Limelight Networks