Remove `NoNaNsFPMath` by using `PatFrag`, we should only use `nnan`. Duplicate tests in `CodeGen/Mips/llvm-ir/nan-fp-attr.ll` are removed.
Remove `NoNaNsFPMath` by using `PatFrag`, we should only use `nnan`. Duplicate tests in `CodeGen/Mips/llvm-ir/nan-fp-attr.ll` are removed.