[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-m68k-linux-cross` running on `suse-gary-m68k-cross` while building `clang,llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/27/builds/7752

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: CodeGen/Mips/subtarget-feature-test.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/bin/clang --target=mips64-linux-gnu -mcpu=i6400 -o /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/tools/clang/test/CodeGen/Mips/Output/subtarget-feature-test.c.tmp -c /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c 2>&1 | /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/bin/FileCheck --allow-empty /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c # RUN: at line 1
+ /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/bin/clang --target=mips64-linux-gnu -mcpu=i6400 -o /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/tools/clang/test/CodeGen/Mips/Output/subtarget-feature-test.c.tmp -c /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c
+ /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/stage1/bin/FileCheck --allow-empty /var/lib/buildbot/workers/suse-gary-m68k-cross/clang-m68k-linux-cross/llvm/clang/test/CodeGen/Mips/subtarget-feature-test.c

--

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


```

</details>

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