[llvm] [Matrix] Use FixedVectorType everywhere in LowerMatrixIntrinsics. NFC (PR #142316)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/20967

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'lld :: MachO/arm64-thunks.s' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
rm -rf /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp; mkdir /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp # RUN: at line 15
+ rm -rf /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp
+ mkdir /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp
/Users/buildbot/buildbot-root/aarch64-darwin/build/bin/llvm-mc -filetype=obj -triple=arm64-apple-darwin /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/lld/test/MachO/arm64-thunks.s -o /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/input.o # RUN: at line 16
+ /Users/buildbot/buildbot-root/aarch64-darwin/build/bin/llvm-mc -filetype=obj -triple=arm64-apple-darwin /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/lld/test/MachO/arm64-thunks.s -o /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/input.o
ld64.lld -arch x86_64 -platform_version macos 11.0 11.0 -syslibroot /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/lld/test/MachO/Inputs/MacOSX.sdk -lSystem -fatal_warnings -arch arm64 -dead_strip -lSystem -U _extern_sym -map /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/thunk.map -o /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/thunk /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/input.o --icf=safe_thunks # RUN: at line 19
+ ld64.lld -arch x86_64 -platform_version macos 11.0 11.0 -syslibroot /Users/buildbot/buildbot-root/aarch64-darwin/llvm-project/lld/test/MachO/Inputs/MacOSX.sdk -lSystem -fatal_warnings -arch arm64 -dead_strip -lSystem -U _extern_sym -map /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/thunk.map -o /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/thunk /Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/input.o --icf=safe_thunks
ld64.lld: error: failed to write output '/Users/buildbot/buildbot-root/aarch64-darwin/build/tools/lld/test/MachO/Output/arm64-thunks.s.tmp/thunk': No space left on device

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/142316