MIPS: Remove uses of CanBeNegative() in HMod.

Port r19878 (74a9002)

BUG=v8:3204
LOG=y
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/197463008

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19910 ce2b1a6d-e550-0410-aec6-3dcde31c8c00