MIPS: Save and restore callee-saved FP registers in cctest/ConvertDToI.

MIPS: Save and restore callee-saved FP registers in cctest/ConvertDToI.

Correctly save and restore FP registers in cctest/ConvertDToI to
avoid accidental register overwriting by the generated code.

Note: This failure is manifested only in R6 mode.

TEST=test/cctest/interpreter/test-interpreter
BUG=

Committed: https://crrev.com/a795aa350f4d62ccbd8ea2ec297e1d844229ba4a
Cr-Commit-Position: refs/heads/master@{#30700}

[akos.palfi.imgtec, 2015-09-11 14:11:15]

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

[akos.palfi.imgtec, 2015-09-11 14:11:16]

PTAL.

[paul.l..., 2015-09-11 14:52:15]

lgtm

[akos.palfi.imgtec, 2015-09-11 15:09:26]

The CQ bit was checked by akos.palfi@imgtec.com

[commit-bot: I haz the power, 2015-09-11 15:09:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1337023002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1337023002/1

[commit-bot: I haz the power, 2015-09-11 15:31:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-11 15:31:26]

Patchset 1 (id:??) landed as
https://crrev.com/a795aa350f4d62ccbd8ea2ec297e1d844229ba4a
Cr-Commit-Position: refs/heads/master@{#30700}