MIPS: remove immediate constraint within CompareAndSwap.

MIPS: remove immediate constraint within CompareAndSwap.

Improper use of immediate constraint is slightly non-optimal
with gcc/gnu-as but causes breakage with clang.

BUG=

Committed: https://crrev.com/eb68d6fe13f13b0697dd2b4ff00df1d7c997669e
Cr-Commit-Position: refs/heads/master@{#26016}

[paul.l..., 2015-01-09 02:17:54]

paul.lind@imgtec.com changed reviewers:
+ akos.palfi@imgtec.com, balazs.kilvady@imgtec.com

[paul.l..., 2015-01-09 02:17:54]

PTAL.

[paul.l..., 2015-01-09 15:31:09]

paul.lind@imgtec.com changed reviewers:
+ danno@chromium.org, jkummerow@chromium.org, machenbach@chromium.org

[paul.l..., 2015-01-09 15:31:09]

PTAL, this change needs v8-team reviewers ....

[balazs.kilvady, 2015-01-09 15:38:46]

LGTM

[Jakob Kummerow, 2015-01-09 19:13:43]

rubberstamp LGTM

[paul.l..., 2015-01-09 19:46:00]

The CQ bit was checked by paul.lind@imgtec.com

[commit-bot: I haz the power, 2015-01-09 19:47:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/841263002/1

[commit-bot: I haz the power, 2015-01-09 20:12:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-09 20:12:40]

Patchset 1 (id:??) landed as
https://crrev.com/eb68d6fe13f13b0697dd2b4ff00df1d7c997669e
Cr-Commit-Position: refs/heads/master@{#26016}