[clang] [llvm] [MIPS] Define SubTargetFeature for i6500 cpu (PR #132907)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-darwin` running on `doug-worker-3` while building `clang,llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/23/builds/8840

<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 'Clang :: CodeGen/Mips/subtarget-feature-test.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/clang --target=mips64-linux-gnu -mcpu=i6400 -o /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/test/CodeGen/Mips/Output/subtarget-feature-test.c.tmp -c /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/CodeGen/Mips/subtarget-feature-test.c 2>&1 | /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/FileCheck --allow-empty /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/CodeGen/Mips/subtarget-feature-test.c # RUN: at line 1
+ /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/clang --target=mips64-linux-gnu -mcpu=i6400 -o /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/tools/clang/test/CodeGen/Mips/Output/subtarget-feature-test.c.tmp -c /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/CodeGen/Mips/subtarget-feature-test.c
+ /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/FileCheck --allow-empty /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/CodeGen/Mips/subtarget-feature-test.c

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/132907