[Driver] clang::driver::getARMCPUForMArch() moved to llvm::Triple::getARMCPUForArch().

Depends on llvm r212846.
Suggested by Eric Christopher.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@212858 91177308-0d34-0410-b5e6-96231b3b80d8