Remove unneeded kernel image from initramfs

[alexgg]

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Contributor checklist

• [ ] Changes have been tested
  • [ ] Covered in automated test suite
  • [ ] Manual test case recorded
• [ ] Change-type present on at least one commit
• [ ] Signed-off-by is present
• [ ] The PR complies with the Open Embedded Commit Patch Message Guidelines

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  • 'Approve' if this change would be acceptable in the codebase (even if there are minor or cosmetic tweaks that could be improved).
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  • 'Comment' if you don't feel you have enough information to decide either way (e.g. if you have major questions, or you don't understand the context of the change sufficiently to fully review yourself, but want to make a comment)