PPC64: [turbofan] Fix DCHECK in AssembleSwap.

PPC64: [turbofan] Fix DCHECK in AssembleSwap.

Fixes these tests in PPC,debug,non-sim

mjsunit/compiler/osr-maze1
mjsunit/compiler/regress-3
mjsunit/regress/regress-crbug-173907
mjsunit/regress/regress-crbug-173907b

R=mbrandy@us.ibm.com

BUG=

Committed: https://crrev.com/1e63ed08ecf587acc2aff9943397abe06bd6f925
Cr-Commit-Position: refs/heads/master@{#27488}

[michael_dawson, 2015-03-26 21:26:46]

Fix some PPC failures in debug mode

[MTBrandyberry, 2015-03-26 21:28:44]

On 2015/03/26 21:26:46, michael_dawson wrote:
> Fix some PPC failures in debug mode

lgtm

[michael_dawson, 2015-03-26 21:49:14]

The CQ bit was checked by michael_dawson@ca.ibm.com

[commit-bot: I haz the power, 2015-03-26 21:49:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1038923003/1

[commit-bot: I haz the power, 2015-03-26 22:12:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-26 22:12:13]

Patchset 1 (id:??) landed as
https://crrev.com/1e63ed08ecf587acc2aff9943397abe06bd6f925
Cr-Commit-Position: refs/heads/master@{#27488}