Use 'vmov Dn[x], ip' instead of 'vmov Sn, ip' to load double immediates.
This patch is only useful for Turbofan as Crankshaft loads double immediates from the constant pool.
This give a little improvement on asm.js benchmarks

R=bmeurer@chromium.org, ulan@chromium.org

BUG=

Review URL: https://codereview.chromium.org/704543002

Cr-Commit-Position: refs/heads/master@{#25146}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25146 ce2b1a6d-e550-0410-aec6-3dcde31c8c00