[llvm] [Thumb1] LivePhysRegs to LiveRegUnits (PR #84474)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

The "squash and merge" button in the GitHub UI only depends on your GitHub account settings, not the "author" line in the commit.  (I don't really want to cherry-pick the patch manually.)

https://github.com/llvm/llvm-project/pull/84474