Revert of MIPS: Fix '[turbofan] Prevent storing signalling NaNs into holey double arrays.' (patchset #2 id:20001 of https://codereview.chromium.org/2171303002/ )

Reason for revert:
This bug has an error in the toolchain.gypi file, the conditions clause is repeated. This has broken the DrMemory builder - see first failing chromium build https://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20Windows%20Builder%20%28DrMemory%29/builds/17857 which included a v8 roll.

For reference the errors are:
gyp: Key 'conditions' repeated at level 11 with key path 'target_defaults.conditions.6.1.target_conditions.0.1.conditions.0.1' while reading C:\b\build\slave\drm-cr\build\src\v8\gypfiles\toolchain.gypi while reading includes of C:\b\build\slave\drm-cr\build\src\v8\src\d8.gyp

gyp: Key 'conditions' repeated at level 11 with key path 'target_defaults.conditions.6.1.target_conditions.0.1.conditions.0.1' while reading C:\b\build\slave\drm-cr\build\src\v8\gypfiles\toolchain.gypi while reading includes of C:\b\build\slave\drm-cr\build\src\v8\src\v8.gyp

gyp: Key 'conditions' repeated at level 11 with key path 'target_defaults.conditions.6.1.target_conditions.0.1.conditions.0.1' while reading C:\b\build\slave\drm-cr\build\src\v8\gypfiles\toolchain.gypi while reading includes of C:\b\build\slave\drm-cr\build\src\v8\samples\samples.gyp

Original issue's description:
> MIPS: Fix '[turbofan] Prevent storing signalling NaNs into holey double arrays.'
>
> Port 6470ddad
>
> On MIPS different signaling NaN values must be used for hardware and simulator targets, even at snapshot generation when always simulator is used.
>
> Original commit message:
> This introduces SilenceNaN operator, which makes sure that we only
> store quiet NaNs into holey arrays. We omit the NaN silencing code
> at instruction selection time if the input is an operation that
> cannot possibly produce signalling NaNs.
>
> BUG=
>
> Committed: https://crrev.com/52f2ceb052f63324050c7a098e4398f510b54763
> Cr-Commit-Position: refs/heads/master@{#38030}

TBR=jarin@chromium.org,machenbach@google.com,akos.palfi@mattakis.com,ivica.bogosavljevic@imgtec.com,marija.antic@imgtec.com,ilija.pavlovic.imgtec@gmail.com,akos.palfi@imgtec.com,machenbach@chromium.org,balazs.kilvady@imgtec.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

TBR=machenbach

Review-Url: https://codereview.chromium.org/2184573002
Cr-Commit-Position: refs/heads/master@{#38037}