Revert of [turbofan] Fixes the code generation for branches on x64 when the condition is Word64Equal. (patchset #1 id:1 of https://codereview.chromium.org/1677503002/ )

Reason for revert:
Code like the example given in the CL description was produced, for example, by code-stub-assembler.cc.

Reverting this, and try to fix the root cause instead.

Original issue's description:
> [turbofan] Fixes the code generation for branches on x64 when the condition is Word64Equal.
>
> Before:
>
> REX.W cmpq r9,r8
> setzl r8l
> movzxbl r8,r8
> REX.W cmpq r8,0x0
> jz 185
>
> After:
>
> REX.W cmpq r9,r8
> jnz 149
>
> Committed: https://crrev.com/75cc8352d06aada2e9131fdae793299ef73fb639
> Cr-Commit-Position: refs/heads/master@{#33784}

TBR=bmeurer@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.

Review URL: https://codereview.chromium.org/1693433002

Cr-Commit-Position: refs/heads/master@{#33884}