Tidy up a few more uses of MF.getFunction()->getName().

Based on CR feedback from r162301 and Craig Topper's refactoring in r162347
here are a few other places that could use the same API (& in one instance drop
a Function.h dependency).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162367 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/RegAllocFast.cpp

@@ -1110,8 +1110,7 @@ void RAFast::AllocateBasicBlock() {
 ///
 bool RAFast::runOnMachineFunction(MachineFunction &Fn) {
   DEBUG(dbgs() << "********** FAST REGISTER ALLOCATION **********\n"
-               << "********** Function: "
-               << ((Value*)Fn.getFunction())->getName() << '\n');
+               << "********** Function: " << Fn.getName() << '\n');
   MF = &Fn;
   MRI = &MF->getRegInfo();
   TM = &Fn.getTarget();