This change is based on a discussion from
https://crrev.com/c/v8/v8/+/2053769/4/src/compiler/machine-operator-reducer.cc#1696
wherein Tobias suggested moving the folding away of ==0 operations out
of the platform-specific instruction selectors and into the
MachineOperatorReducer. I noticed that CommonOperatorReducer already
handles some very similar cases, so I have tried putting the ==0 folding
into CommonOperatorReducer instead. I'm happy to move it into
MachineOperatorReducer if that's better; I still don't have a very good
understanding of how roles are separated among reducers.

Change-Id: Ia0285bd9fafeef29d87cc88654bd6d355d467e8f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2076498
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66688}