[llvm] [RISCV] Teach getIntImmCostInst about (X & -(1 << C1) & 0xffffffff) == C2 << C1 (PR #160163)

[Piotr Fusik via llvm-commits]

https://github.com/pfusik approved this pull request.

Since you renamed the function, you need to update its name at the call site.
Otherwise LGTM.

https://github.com/llvm/llvm-project/pull/160163