Make CodePlacementOpt align loops, rather than loop headers. The

Make CodePlacementOpt align loops, rather than loop headers. The
header is just the entry block to the loop, and it needn't be at
the top of the loop in the code layout.

Remove the code that suppressed loop alignment for outer loops,
so that outer loops are aligned.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84158 91177308-0d34-0410-b5e6-96231b3b80d8