TBAA: use the same format for scalar TBAA and struct-path aware TBAA.

Struct-path aware TBAA generates tags to specify the access path,
while scalar TBAA only generates tags to scalar types.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191586 91177308-0d34-0410-b5e6-96231b3b80d8