[llvm] [Matrix] Hoist finalizeLowering into caller. NFC (PR #143038)

[Jon Roelofs via llvm-commits]

jroelofs wrote:

> Hi @jroelofs, This patch broke us downstream. Can you please provide some information as to what the benefits are provided by this change?

The idea for it came from review feedback from @fhahn in https://github.com/llvm/llvm-project/pull/141869#discussion_r2129177420: we call finalizeLowering in all of the Visit* methods, so it _should_ be NFC to hoist that into the caller. Can you share a small reproducer?

https://github.com/llvm/llvm-project/pull/143038