[llvm] [RISCV] Remove what appears to be an unnecessary check for LMUL_8 in getSingleShuffleSrc. (PR #127250)

[Philip Reames via llvm-commits]

preames wrote:

> This was changed in

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LGTM w/that addressed or the description otherwise reworked.

https://github.com/llvm/llvm-project/pull/127250