We should track against `stable/linux.git` and not `torvalds/linux`

[bleggett]

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

is where most of the actual released LTS tags come from, so we should probably track that instead, torvalds is not the upstream LTS release branch and does not carry actual LTS release tags, and 90% of what we do in the product is necessarily based strictly off of upstream LTS releases, not bleeding edge.

Specifically, all of our LTS branches in this repo should be based off of an explicit upstream X.Y.Z tag from stable/linux.git, not a random commit from torvalds, ex: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tag/?h=v6.18.53