[llvm] [RISCV] Remove artificial restriction on ShAmt from (shl (and X, C2), C) -> (slli (srliw X, C3), C3+C) isel. (PR #143010)

[Piotr Fusik via llvm-commits]

pfusik wrote:

LGTM, modulo the commit message. I think you are relaxing the `(shl (and X, C2), C) -> (srli (slli X, C4), C4-C)` pattern.

https://github.com/llvm/llvm-project/pull/143010