MachineFunction: Return reference for getFrameInfo(); NFC

getFrameInfo() never returns nullptr so we should use a reference
instead of a pointer.

llvm-svn: 277017
diff --git a/llvm/lib/Target/Mips/MipsInstrInfo.cpp b/llvm/lib/Target/Mips/MipsInstrInfo.cpp
index 91f107f..1f38ca6 100644
--- a/llvm/lib/Target/Mips/MipsInstrInfo.cpp
+++ b/llvm/lib/Target/Mips/MipsInstrInfo.cpp
@@ -58,7 +58,7 @@
 MipsInstrInfo::GetMemOperand(MachineBasicBlock &MBB, int FI,
                              MachineMemOperand::Flags Flags) const {
   MachineFunction &MF = *MBB.getParent();
-  MachineFrameInfo &MFI = *MF.getFrameInfo();
+  MachineFrameInfo &MFI = MF.getFrameInfo();
   unsigned Align = MFI.getObjectAlignment(FI);
 
   return MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(MF, FI),