[utils/ClangDataFormat.py] Don't use lldb.frame directly, get the frame from the value.

Some lldb changes made lldb.frame not set until a script is invoked, which made the
formatters not working after a restart.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172017 91177308-0d34-0410-b5e6-96231b3b80d8