Set mayLoad or mayStore flags for SC and LL in order to prevent LICM from

Set mayLoad or mayStore flags for SC and LL in order to prevent LICM from
moving them out of the loop. Previously, stores and loads to a stack frame
object were inserted to accomplish this. Remove the code that was needed to do
this. Patch by Sasa Stankovic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135415 91177308-0d34-0410-b5e6-96231b3b80d8