Revert r368509 "[CodeGen] Do the Simple Early Return in block-placement pass...

Revert r368509 "[CodeGen] Do the Simple Early Return in block-placement pass to optimize the blocks"

> In `block-placement` pass, it will create some patterns for unconditional we can do the simple early retrun.
> But the `early-ret` pass is before `block-placement`, we don't want to run it again.
> This patch is to do the simple early return to optimize the blocks at the last of `block-placement`.
>
> Reviewed By: efriedma
>
> Differential Revision: https://reviews.llvm.org/D63972

This also revertes follow-ups r368514 and r368532.

llvm-svn: 368560