compiler-rt: use fp_t instead of long double, for consistency

Most builtins accepting or returning long double use the fp_t typedef.
Change the remaining few cases to do so.

Differential Revision:	https://reviews.llvm.org/D35034

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@371400 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed