Disable ARM partial flag dependency optimization at -Oz

Disable ARM partial flag dependency optimization at -Oz

To not over constrain the scheduler for ARM in thumb mode, some optimizations  for code size reduction, specific to ARM thumb, are blocked when they add a dependency (like write after read dependency).

Disables this check when code size is the priority, i.e., code is compiled with -Oz.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170462 91177308-0d34-0410-b5e6-96231b3b80d8