[X86] Replace unnecessary CVTPS2PI/CVTPS2DQ overrides with better base class defs

Broadwell/Haswell were completely overriding the WriteCvtPD2I class defs - we can remove those overrides entirely by just choosing better class defs.

Also fixes the scheduler for a missing YMM folded case - confirmed with Agner + uops.info that the port usage is correct