This reverts commit ada64800.

Reason for revert: Failure with slow dchecks: https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux%20-%20debug/20982

Original change's description:
> [Liftoff] Fix register use count
> 
> In {SetLocalFromStackSlot}, we decrement the use count of the register
> in the target slot without updating this slot, and then call
> {GetUnusedRegister}. At that point, the register use counts do not
> match the cache state, which leads to errors later on.
> This CL fixes this by marking the target slot as a stack slot after
> reducing the register use count.
> 
> It also adds a Validation which helped to find that error and will
> catch similar errors earlier.
> 
> R=​titzer@chromium.org
> 
> Bug: chromium:854050, v8:6600
> Change-Id: I74d3a5aa947ec4247d7b4557567f642bf4082316
> Reviewed-on: https://chromium-review.googlesource.com/1111958
> Reviewed-by: Ben Titzer <titzer@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#53976}

TBR=titzer@chromium.org,clemensh@chromium.org

Change-Id: I5b8d8d405dcd7f82ee431cba290419425b9859a1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:854050, v8:6600
Reviewed-on: https://chromium-review.googlesource.com/1112277Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53979}