Add TargetInstrInfo interface isAsCheapAsAMove.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214158 91177308-0d34-0410-b5e6-96231b3b80d8
Implement AArch64 TTI interface isAsCheapAsAMove.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214159 91177308-0d34-0410-b5e6-96231b3b80d8