Revert r224739: Debug info: Teach SROA how to update debug info for
fragmented variables.

This caused codegen to start crashing when we built somewhat large
programs with debug info and optimizations. 'check-msan' hit in, and
I suspect a bootstrap would as well. I mailed a test case to the
review thread.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224750 91177308-0d34-0410-b5e6-96231b3b80d8