[CodeGen] Promote FMINNAN/FMAXNAN like other binops.

We think it's OK to generate half fminnan because it's legal for the
transform-to type (f32; r245196). However, PromoteFloatRes was missing
the case; simply promote like the other binops, including minnum.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@271317 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed