ARM64: Range based for loop in ARM64PromoteConstant pass

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205748 91177308-0d34-0410-b5e6-96231b3b80d8
Tidy up comments a bit.

Punctuation, grammar, formatting, etc..

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205749 91177308-0d34-0410-b5e6-96231b3b80d8