Fixes extract when imms = 0 because a left shift of 64 is not valid.

R=rodolph.perfetta@arm.com, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/286193004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21459 ce2b1a6d-e550-0410-aec6-3dcde31c8c00