[llvm] [AMDGPU][CodeGen] Fix `S_NOP` insertion during `S_SET_VGPR_MSB` placement (PR #209525)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-mlir-rhel-clang` running on `ppc64le-mlir-rhel-test` while building `llvm` at step 6 "test-build-check-mlir-build-only-check-mlir".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/47996

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-check-mlir-build-only-check-mlir) failure: 1200 seconds without output running [b'ninja', b'check-mlir'], attempting to kill
...
PASS: MLIR-Unit :: Dialect/SparseTensor/./MLIRSparseTensorTests/8/210 (4372 of 4381)
PASS: MLIR-Unit :: Dialect/SparseTensor/./MLIRSparseTensorTests/78/210 (4373 of 4381)
PASS: MLIR-Unit :: Dialect/SparseTensor/./MLIRSparseTensorTests/70/210 (4374 of 4381)
PASS: MLIR-Unit :: Dialect/SparseTensor/./MLIRSparseTensorTests/7/210 (4375 of 4381)
PASS: MLIR-Unit :: Dialect/SparseTensor/./MLIRSparseTensorTests/97/210 (4376 of 4381)
PASS: MLIR-Unit :: Dialect/SparseTensor/./MLIRSparseTensorTests/98/210 (4377 of 4381)
PASS: MLIR :: Pass/pipeline-parsing.mlir (4378 of 4381)
PASS: MLIR :: Pass/pipeline-options-parsing.mlir (4379 of 4381)
PASS: MLIR :: mlir-tblgen/rewriter-errors.td (4380 of 4381)
PASS: MLIR :: mlir-tblgen/llvm-intrinsics.td (4381 of 4381)
command timed out: 1200 seconds without output running [b'ninja', b'check-mlir'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=2364.796323

```

</details>

https://github.com/llvm/llvm-project/pull/209525