MachineFunction: Return reference from getFunction(); NFC

The Function can never be nullptr so we can return a reference.

llvm-svn: 320884
diff --git a/llvm/lib/Target/Hexagon/HexagonGenMux.cpp b/llvm/lib/Target/Hexagon/HexagonGenMux.cpp
index dc1cdc8..5a001d6 100644
--- a/llvm/lib/Target/Hexagon/HexagonGenMux.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonGenMux.cpp
@@ -368,7 +368,7 @@
 }
 
 bool HexagonGenMux::runOnMachineFunction(MachineFunction &MF) {
-  if (skipFunction(*MF.getFunction()))
+  if (skipFunction(MF.getFunction()))
     return false;
   HII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
   HRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();