dpdk: allow specifying RSS hash function flags in the config

[lukashino]

Make sure these boxes are signed before submitting your Pull Request -- thank you.

• [X] I have read the contributing guide lines at https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Contributing
• [X] I have signed the Open Information Security Foundation contribution agreement at https://suricata.io/about/contribution-agreement/
• [X] I have updated the user guide (in doc/userguide/) to reflect the changes made (if applicable)

Link to redmine ticket:

Redmine ticket: #5400

[codecov[bot]]

Codecov Report

Merging #7854 (5854106) into master (fe91506) will decrease coverage by 0.14%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7854      +/-   ##
==========================================
- Coverage   75.99%   75.85%   -0.15%     
==========================================
  Files         665      665              
  Lines      185963   185962       -1     
==========================================
- Hits       141327   141056     -271     
- Misses      44636    44906     +270     

Flag	Coverage Δ
fuzzcorpus	60.48% <ø> (-0.37%)	:arrow_down:
suricata-verify	52.49% <ø> (-0.02%)	:arrow_down:
unittests	60.68% <ø> (-0.01%)	:arrow_down:

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[victorjulien]

Merged in #7966, thanks!