MIPS: Add cvt_d_s to disassembler.

BUG=
R=dusan.milosavljevic@imgtec.com

Review URL: https://codereview.chromium.org/605113002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24343 ce2b1a6d-e550-0410-aec6-3dcde31c8c00