Add support for krait cpu in llvm::sys::getHostCPUName()

Recently, support for krait cpu was added. This commit extends getHostCPUName()
to return krait as cpu for the APQ8064 (a Krait 300).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197792 91177308-0d34-0410-b5e6-96231b3b80d8