[mips] Fix Load/StoreGlobalContext stubs.

[mips] Fix Load/StoreGlobalContext stubs.

Fix invalid tail calls and wrong context register.

R=ishell@chromium.org

Committed: https://crrev.com/dd1a26de5c8ab9d4b539a33a2ec6a8dac877b243
Cr-Commit-Position: refs/heads/master@{#29844}

[Benedikt Meurer, 2015-07-24 12:12:18]

Hey Igor,

Here's the combined fix that you suggested.
Please take a look.

Thanks,
Benedikt

[Igor Sheludko, 2015-07-24 12:27:56]

The CQ bit was checked by ishell@chromium.org

[Igor Sheludko, 2015-07-24 12:27:57]

lgtm

[commit-bot: I haz the power, 2015-07-24 12:28:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1257603004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1257603004/1

[commit-bot: I haz the power, 2015-07-24 12:37:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-24 12:37:26]

Patchset 1 (id:??) landed as
https://crrev.com/dd1a26de5c8ab9d4b539a33a2ec6a8dac877b243
Cr-Commit-Position: refs/heads/master@{#29844}

[paul.l..., 2015-07-26 04:37:47]

Sorry for all the problems, I'd missed that this was behind the flag, so my
testing was useless. Igor, Benedikt, thanks a lot for fixing these! One more fix
coming.