When writing kernel, save the branches til the end. They are still put in the "right...

When writing kernel, save the branches til the end. They are still put in the "right place" in the schedule, but sometimes when folding to make a kernel instructions are added between branches. This is wrong. To avoid this, we handle branches special.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18450 91177308-0d34-0410-b5e6-96231b3b80d8