[llvm] [MIPS] Add Scheduling model for MIPS i6400 and i6500 CPUs (PR #132704)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-nvptx-nvidia-ubuntu` running on `as-builder-7` while building `llvm` at step 6 "test-build-unified-tree-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/180/builds/17043

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

```
Step 6 (test-build-unified-tree-check-llvm) failure: test (failure)
******************** TEST 'LLVM :: tools/llvm-mca/Mips/i6400.s' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/build/bin/llvm-mca -mtriple=mips64el -mcpu=i6400 --mattr=msa -iterations=1 < /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/llvm-project/llvm/test/tools/llvm-mca/Mips/i6400.s | /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/build/bin/FileCheck /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/llvm-project/llvm/test/tools/llvm-mca/Mips/i6400.s # RUN: at line 2
+ /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/build/bin/llvm-mca -mtriple=mips64el -mcpu=i6400 --mattr=msa -iterations=1
+ /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/build/bin/FileCheck /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/llvm-project/llvm/test/tools/llvm-mca/Mips/i6400.s
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/build/bin/llvm-mca: unable to get target for 'mips64el', see --version and --triple.FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/build/bin/FileCheck /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx-nvidia-ubuntu/llvm-project/llvm/test/tools/llvm-mca/Mips/i6400.s

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/132704