[llvm] [Windows] Allow legalizing LDEXP_F128 and FREXP_F128 with libcalls (PR #148326)

[Matt Arsenault via llvm-commits]

arsenm wrote:

Changing the failure mode from legalization failure to compiles to function with the wrong type isn't an improvement. Don't we have an inline expansion for these to fall back on?

https://github.com/llvm/llvm-project/pull/148326