Apply tentative llvm fix for avoiding fma on PowerPC SPE

Merge llvm review D77558, by Justin Hibbits:

  PowerPC: Don't hoist float multiply + add to fused operation on SPE

  SPE doesn't have a fmadd instruction, so don't bother hoisting a
  multiply and add sequence to this, as it'd become just a library call.
  Hoisting happens too late for the CTR usability test to veto using the CTR
  in a loop, and results in an assert "Invalid PPC CTR loop!".

Reported by:		alfredo
Obtained from:		https://reviews.llvm.org/D77558
MFC after:		3 days

contrib/llvm-project/llvm/lib/Target/PowerPC/PPCISelLowering.cpp

@@ -16623,6 +16623,8 @@ bool PPCTargetLowering::isFMAFasterThanFMulAndFAdd(const MachineFunction &MF,
 
 bool PPCTargetLowering::isFMAFasterThanFMulAndFAdd(const Function &F,
                                                    Type *Ty) const {
+  if (Subtarget.hasSPE())
+    return false;
   switch (Ty->getScalarType()->getTypeID()) {
   case Type::FloatTyID:
   case Type::DoubleTyID: