[llvm] [RISCV] Avoid early split for fixed-length VECTOR_DEINTERLEAVE (PR #226453)

[via llvm-commits]

github-actions[bot] wrote:

test-suite diff from 675c1cfa5d925232db882942674a40de41654bc5...9d6d39a78a1effb8b20e92d845f9806913a46e0d: https://github.com/llvm/llvm-project/actions/runs/36130537462/artifacts/10867297409

Statistics: https://github.com/llvm/llvm-project/actions/runs/36130537462/artifacts/10866982737

## riscv64-linux-gnu `-march=rva23u64 -O3`
| ('Program', '')    |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:-------------------|-------------------------:|-------------------------:|-------------------------:|
| Geomean difference |                      nan |                      nan |                        0 |
## aarch64-linux-gnu `-march=armv9-a -O3`
| ('Program', '')    |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:-------------------|-------------------------:|-------------------------:|-------------------------:|
| Geomean difference |                      nan |                      nan |                        0 |
## x86_64-linux-gnu `-march=x86-64-v3 -O3`
| ('Program', '')    |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:-------------------|-------------------------:|-------------------------:|-------------------------:|
| Geomean difference |                      nan |                      nan |                        0 |


https://github.com/llvm/llvm-project/pull/226453