R600/SI: Fix verifier errors from the SIAnnotateControlFlow pass

R600/SI: Fix verifier errors from the SIAnnotateControlFlow pass

This pass was generating 'Instruction does not dominate all uses!'
errors for programs which had loops with a condition variable that
depended on the result of a phi instruction from outside of the loop.

The pass was inserting new phi nodes outside of the loop which used values
defined inside the loop.

http://bugs.freedesktop.org/show_bug.cgi?id=90056

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236306 91177308-0d34-0410-b5e6-96231b3b80d8