[llvm] [test] Add missing tests for Arm frexpf128 and Mips ldexpf128 (PR #148793)

[Trevor Gross via llvm-commits]

tgross35 wrote:

@arsenm could you review? I figured you would get to these at some point based on your recent work, I had them on a branch already.

See also https://github.com/llvm/llvm-project/pull/148794

https://github.com/llvm/llvm-project/pull/148793