[llvm] DAG: Skip 0 sign handling in minimum/maximum lowering for _ieee case (PR #91326)

[Min-Yih Hsu via llvm-commits]

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

LGTM.
I don't know if the PowerPC change is correct though.

https://github.com/llvm/llvm-project/pull/91326