[mips][sched] Renamed II_FsqrtSingle and II_FsqrtDouble to II_SQRT_S and II_SQRT_D respectively

No functional change



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199741 91177308-0d34-0410-b5e6-96231b3b80d8