Fix the compilation error for turbofan unsupported platform.

Fix the compilation error for turbofan unsupported platform.

  Fix the compilation error for turbofan unsupported platform. The Linkage::GetOsrValuePosition()
  function is implemented in linkage-impl.h. And this file is included by different platform specific
  file separately. This leads to compilation error for turbofan unsupported platform.

  The fix is adding one dummy implementation in linkage.cc.

BUG=

Committed: https://crrev.com/728b39573cc1512c738c782b26f990a6838ec51e
Cr-Commit-Position: refs/heads/master@{#26041}

[chunyang.dai, 2015-01-13 12:21:44]

chunyang.dai@intel.com changed reviewers:
+ titzer@chromium.org

[chunyang.dai, 2015-01-13 12:22:58]

hi, 
PTAL.
thanks

[titzer, 2015-01-13 12:44:28]

lgtm

[titzer, 2015-01-13 12:44:31]

The CQ bit was checked by titzer@chromium.org

[commit-bot: I haz the power, 2015-01-13 12:45:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/848873002/1

[commit-bot: I haz the power, 2015-01-13 13:12:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-13 13:12:41]

Patchset 1 (id:??) landed as
https://crrev.com/728b39573cc1512c738c782b26f990a6838ec51e
Cr-Commit-Position: refs/heads/master@{#26041}