[SPARC] Allows inlining of atomics for Sparc32 with appropriate store barrier.

The final change is required to extend the back-end's AtomicExpandPass that was implemented for Sparc (64 bit) and later extended for Sparc (32 bit).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@274012 91177308-0d34-0410-b5e6-96231b3b80d8