Do not put instrumentation counters before phis in ObjC for-in loops.

We still don't use the PGO to set branch weights for these loops, but at
least this keeps the compiler from crashing. <rdar://problem/16137778>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202002 91177308-0d34-0410-b5e6-96231b3b80d8