eliminate the now-unneeded context argument of MBB::getSymbol()

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98451 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineFunction.h

@@ -33,6 +33,7 @@ class MachineRegisterInfo;
 class MachineFrameInfo;
 class MachineConstantPool;
 class MachineJumpTableInfo;
+class MCContext;
 class Pass;
 class TargetMachine;
 class TargetRegisterClass;