Revert "[WebAssembly] Combine i128 to v16i8 for setcc & expand memcmp for 16...

Revert "[WebAssembly] Combine i128 to v16i8 for setcc & expand memcmp for 16 byte loads with simd128" (#153360)

Reverts llvm/llvm-project#149461

The first test w/ memcmp in `test/neon/test_neon_wasm_simd.cpp` in the
Emscripten test suite has failed. This PR applies a revert so I can take
a closer look at it

Test case link:
https://github.com/emscripten-core/emscripten/blob/main/test/neon/test_neon_wasm_simd.cpp

Compile option: `em++ test_neon_wasm_simd.cpp -O2 -mfpu=neon -msimd128
-o something.js`

Original comment report:
https://github.com/llvm/llvm-project/pull/149461#issuecomment-3181652746