kernel: T6788: Added patch to fix sequence adjustment for FTP DNAT

[AndriiFullroot]

Change summary

The patch adds seqadj initialization for NATed conntrack.
This fixes access to FTP servers "behind" the NAT router.
The patch itself was proposed to the kernel and was accepted.
In future versions it should be included into the kernel.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

https://vyos.dev/T6788

Related PR(s)

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

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[github-actions]

👍
No issues in PR Title / Commit Title

[dmbaturin]

I trust Andrii's judgement and testing, even if I'm not familiar with the code. Let's get it in to give it more testing.

[sever-sever]

Fix FTP kernel