Rewrite overflow instructions in order to allow branch
poisoning.

Change-Id: I5f97808c7eac08927243780a0ae0c48f6de0c45b
Reviewed-on: https://chromium-review.googlesource.com/964321
Commit-Queue: Ivica Bogosavljevic <ivica.bogosavljevic@mips.com>
Reviewed-by: Sreten Kovacevic <sreten.kovacevic@mips.com>
Cr-Commit-Position: refs/heads/master@{#51984}