[turbofan] Fix missing machine type for float32/float64 array accesses.

TEST=mjsunit/asm
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/703883002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25128 ce2b1a6d-e550-0410-aec6-3dcde31c8c00