[llvm] [NFC] Add a pre-commit test case for #111696 (PR #136730)

[Amy Kwan via llvm-commits]

================
@@ -0,0 +1,178 @@
+;; Test ppc-vsx-fma-mutate pass with -schedule-ppc-vsx-fma-mutation-early do not hosit some xxspltiw instruction.
----------------
amy-kwan wrote:

```suggestion
;; Tests that the ppc-vsx-fma-mutate pass with the schedule-ppc-vsx-fma-mutation-early pass does not hoist xxspltiw out of loops.
```
Is this comment accurate?

https://github.com/llvm/llvm-project/pull/136730