The test for a SMI before the write barrier tested the wrong register:
r0 = target context address
r1 = value to be written

This change fixes the SMI test and tests r1 instead of r0.

Review URL: http://codereview.chromium.org/384085

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3299 ce2b1a6d-e550-0410-aec6-3dcde31c8c00