[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 `clang-cmake-x86_64-avx512-linux` running on `avx512-intel64` while building `clang,llvm` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/133/builds/13540

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

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: CodeGen/Mips/subtarget-feature-test.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/stage1/bin/clang --target=mips64-linux-gnu -mcpu=i6400 -o /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/stage1/tools/clang/test/CodeGen/Mips/Output/subtarget-feature-test.c.tmp -c /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c 2>&1 | /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/stage1/bin/FileCheck --allow-empty /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c # RUN: at line 1
+ /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/stage1/bin/clang --target=mips64-linux-gnu -mcpu=i6400 -o /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/stage1/tools/clang/test/CodeGen/Mips/Output/subtarget-feature-test.c.tmp -c /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c
+ /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/stage1/bin/FileCheck --allow-empty /localdisk2/buildbot/llvm-worker/clang-cmake-x86_64-avx512-linux/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c

--

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


```

</details>

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