[llvm] [RISCV] Remove intrinsic declarations in tests, NFC (PR #167474)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-mlir-rhel-clang` running on `ppc64le-mlir-rhel-test` while building `llvm` at step 3 "clean-build-dir".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/33897

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

```
Step 3 (clean-build-dir) failure: Delete failed. (failure) (timed out)
Step 5 (build-check-mlir-build-only) failure: build (failure) (timed out)
...
7.600 [4180/174/115] Building CXX object lib/LineEditor/CMakeFiles/LLVMLineEditor.dir/LineEditor.cpp.o
7.602 [4180/173/116] Building CXX object third-party/unittest/CMakeFiles/llvm_gtest.dir/googlemock/src/gmock-all.cc.o
7.603 [4180/172/117] Building CXX object lib/FileCheck/CMakeFiles/LLVMFileCheck.dir/FileCheck.cpp.o
7.605 [4180/171/118] Building CXX object third-party/unittest/CMakeFiles/llvm_gtest_main.dir/UnitTestMain/TestMain.cpp.o
7.606 [4180/170/119] Building CXX object utils/FileCheck/CMakeFiles/FileCheck.dir/FileCheck.cpp.o
7.607 [4180/169/120] Building CXX object utils/not/CMakeFiles/not.dir/not.cpp.o
7.608 [4180/168/121] Building CXX object utils/split-file/CMakeFiles/split-file.dir/split-file.cpp.o
7.608 [4180/167/122] Linking CXX static library lib/libLLVMDemangle.a
7.626 [4180/166/123] Building CXX object third-party/unittest/CMakeFiles/llvm_gtest.dir/googletest/src/gtest-all.cc.o
7.759 [4180/165/124] Linking CXX static library lib/libMLIRTableGen.a
command timed out: 1200 seconds without output running [b'ninja', b'check-mlir-build-only'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1208.324697

```

</details>

https://github.com/llvm/llvm-project/pull/167474