MIPS: Fixed environment handling for LFlooringDivI.

Port c16b8f6cbbe295abf3fab2f6b9f4a4632db4cf6b

TEST=mjsunit/regress/regress-437765
BUG=

Review URL: https://codereview.chromium.org/750213003

Cr-Commit-Position: refs/heads/master@{#25671}