Revert r216803 "[MachineSinking] Clear kill flag of all operands at all their uses."

This reverts commit r216803, because it might have broken the buildbot.
The issue is tracked in PR20842.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217120 91177308-0d34-0410-b5e6-96231b3b80d8