Revert "AArch64CollectLOH: Rewrite as block-local analysis."

This is not always behaving as expected as it turns out block live-in
lists are only correct most of the time. Still waiting for reviews on
https://reviews.llvm.org/D27559 to have them correct all of the time.

See also http://llvm.org/PR31361, rdar://25117107

This reverts commit r288567.
This reverts commit r288561.

llvm-svn: 289570