ixgbe.4: Add flow director CAVEAT
Flow-director support is not fully implemented and will cause
errors if enabled. Mention this in the ixgbe(4) manual.
PR: 202663
Co-authored-by: Alexander Ziaee <concussious@runbox.com>
Pull Request: https://github.com/freebsd/freebsd-src/pull/1493
(cherry picked from commit 20b823a59bc7419a6f93ec5097bd5ee524c20981)