Revert "cpu-fusion: Disabled fusion of partial reductions."
Revert "cpu-fusion: Disabled fusion of partial reductions."

Not allowing partial reductions lead to other performance issues.

This reverts commit 4a928f470916cfaa06a43cb7503a84e310283acd.

madsbk/bohrium,bh107/bohrium,bh107/bohrium,madsbk/bohrium,bh107/bohrium,bh107/bohrium,madsbk/bohrium,madsbk/bohrium