[llvm] Reapply "[ARM] Use addLiveIns method instead of manually adding live ins (#87560)" (PR #96448)

[David Green via llvm-commits]

davemgreen wrote:

>From what I can tell from https://reviews.llvm.org/D66319 this should be OK, as it was added mostly to catch verification errors and as far as I understand not adding subregs is OK. @efriedma-quic any objections?

https://github.com/llvm/llvm-project/pull/96448