[llvm] [VPlan] Account for early-exit dispatch blocks when updating LI. (PR #185618)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

LGTM, the new pass and test diffs make sense to me.

Although just for my own understanding why were we failing to remove the vector.early.exit.* blocks from the loops to begin with?

https://github.com/llvm/llvm-project/pull/185618