[IR] Replace all uses of CallBase::getCalledValue() with getCalledOperand().

This method has been commented as deprecated for a while. Remove
it and replace all uses with the equivalent getCalledOperand().

I also made a few cleanups in here. For example, to removes use
of getElementType on a pointer when we could just use getFunctionType
from the call.

Differential Revision: https://reviews.llvm.org/D78882
diff --git a/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp b/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
index 70bb272..86fbb4b 100644
--- a/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
@@ -52,7 +52,7 @@
 
   // Try looking through a bitcast from one function type to another.
   // Commonly happens with calls to objc_msgSend().
-  const Value *CalleeV = CB.getCalledValue()->stripPointerCasts();
+  const Value *CalleeV = CB.getCalledOperand()->stripPointerCasts();
   if (const Function *F = dyn_cast<Function>(CalleeV))
     Info.Callee = MachineOperand::CreateGA(F, 0);
   else