[Power9] Add __float128 library call for frem

Power 9 does not have a hardware instruction for frem but we can call fmodf128.

Differential Revision: https://reviews.llvm.org/D48552

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336406 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed