Revert of MIPS: [turbofan] Fix addition for deoptimization. (patchset #3 id:40001 of https://codereview.chromium.org/2102063002/ )

Reason for revert:
This workaround is no longer needed, port of e60c4053 fixes the issue.

Original issue's description:
> MIPS: [turbofan] Fix addition for deoptimization.
>
> In turbofan, after an addition operation where the same register is the
> output and both inputs, if deoptimization is performed the input is
> overwritten with the output value and the final result is not correct.
> This is fixed by restoring the original value of the input before
> deoptimization.
>
> BUG=
> TEST=mjsunit/regress/regress-int32-truncation
>
> Committed: https://crrev.com/99385e8e4bcef1f333ede61c936528bfc0c8ecfa
> Cr-Commit-Position: refs/heads/master@{#37524}

TBR=akos.palfi@imgtec.com,balazs.kilvady@imgtec.com,ivica.bogosavljevic@imgtec.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review-Url: https://codereview.chromium.org/2129083003
Cr-Commit-Position: refs/heads/master@{#37612}