[llvm] [RISCV] Fix coalesced vsetvli's AVL LiveInterval not always being shrunk (PR #98286)

[Philip Reames via llvm-commits]

preames wrote:

Sorry for the confusion, you're right about DefReg vs OldVLReg.  I think you're also right about the early continue being the trigger, but looking at that code, it looks like we're also missing the ADDI prune in that case as well.  Maybe pull out a lambda for prepareToDelete which does all the LIS fixup, ADDI deletion, and addition to the ToDelete list?

https://github.com/llvm/llvm-project/pull/98286