[llvm] [DAGCombine] Remove oneuse restrictions for RISCV in folding (shl (add_nsw x, c1)), c2) and folding (shl(sext(add x, c1)), c2) in some scenarios (PR #101294)

[Simon Pilgrim via llvm-commits]

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

LGTM

https://github.com/llvm/llvm-project/pull/101294