[llvm] [offload] Remove redundant checks in MappingInfoTy::lookupMapping (PR #127638)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

Makes sense, just eliminating some checks if we already know the lower / upper bound. Should be good so long as it passes the tests.

https://github.com/llvm/llvm-project/pull/127638