[nfc][codegen] Move RegisterBank[Info].cpp under CodeGen

Layering-wise, it seems RegisterBank stuff fits under CodeGen, like
other target abstraction.
In particular, TargetSubtargetInfo has a getRegBankInfo member, but
using that object requires making sure GlobalISel is linked, which is
not always the case (e.g. llvm-jitlink doesn't).

Differential Revision: https://reviews.llvm.org/D119053

llvm/lib/CodeGen/CMakeLists.txt

@@ -188,6 +188,8 @@ add_llvm_component_library(LLVMCodeGen
   RegUsageInfoPropagate.cpp
   ReplaceWithVeclib.cpp
   ResetMachineFunctionPass.cpp
+  RegisterBank.cpp
+  RegisterBankInfo.cpp
   SafeStack.cpp
   SafeStackLayout.cpp
   ScheduleDAG.cpp

llvm/lib/CodeGen/GlobalISel/CMakeLists.txt

@@ -22,8 +22,6 @@ add_llvm_component_library(LLVMGlobalISel
   LostDebugLocObserver.cpp
   MachineIRBuilder.cpp
   RegBankSelect.cpp
-  RegisterBank.cpp
-  RegisterBankInfo.cpp
   Utils.cpp
 
   ADDITIONAL_HEADER_DIRS