[llvm] [RISCV][llvm-mca] Use correct LMUL and SEW for strided loads and stores (PR #76869)

[Michael Maitland via llvm-commits]

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+# NOTE: Assertions have been autogenerated by utils/update_mca_test_checks.py
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michaelmaitland wrote:

I think it would make most sense to have a directory for each schedule model. What do you think about me fixing that in a follow up patch, as the test here is in the correct directory already?

https://github.com/llvm/llvm-project/pull/76869