Revert "[InstCombine] [InstCombine] Canonicalize (-X s/ Y) to -(X s/ Y)."

This reverts commit 1383a916.

sdiv-canonicalize.ll fails after this revision. The fold needs to be
moved outside the branch handling constant operands. However when this
is done there are further test changes, so I'm reverting this in the
meantime.

llvm-svn: 358026