[clang] [llvm] [LoongArch][BF16] Add support for the __bf16 type (PR #142548)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-gcc-ubuntu-no-asserts` running on `doug-worker-6` while building `clang,llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/202/builds/1690

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

```
Step 6 (test-build-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: lit :: unique-output-file.py (88707 of 88717)
PASS: lit :: usage.py (88708 of 88717)
PASS: lit :: use-llvm-tool.py (88709 of 88717)
PASS: lit :: selecting.py (88710 of 88717)
PASS: lit :: xunit-output-report-failures-only.py (88711 of 88717)
PASS: lit :: xunit-output.py (88712 of 88717)
PASS: lit :: xfail-cl.py (88713 of 88717)
PASS: lit :: shtest-timeout.py (88714 of 88717)
PASS: lit :: shtest-define.py (88715 of 88717)
PASS: lit :: shtest-shell.py (88716 of 88717)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=3873.821627

```

</details>

https://github.com/llvm/llvm-project/pull/142548