[llvm] [RISCV] Don't vectorize for loops with small trip count (PR #132176)

[Luke Lau via llvm-commits]

lukel97 wrote:

It doesn't seem to affect most benchmarks, so overall quite neutral https://lnt.lukelau.me/db_default/v4/nts/358?show_delta=yes&show_previous=yes&show_stddev=yes&show_mad=yes&show_all=yes&show_all_samples=yes&show_sample_counts=yes&show_small_diff=yes&num_comparison_runs=0&test_filter=&test_min_value_filter=&aggregation_fn=min&MW_confidence_lv=0.05&compare_to=360&submit=Update

https://github.com/llvm/llvm-project/pull/132176