Subzero, MIPS32: Atomic intrinsics fixes

This patch introduces changes to the MIPS32 intrinsic functions to
comply with PNaCl smoke tests.

Also made a change regarding addressing relative to frame pointer,
since it differs in MIPS compared to ARM and x86.

R=stichnot@chromium.org

Patch from Stefan Maksimovic <makdstefan@gmail.com>.

Review-Url: https://codereview.chromium.org/2619363003 .
5 files changed