x86: fold VFPCLASSP{D,S} templates

x86: fold VFPCLASSP{D,S} templates

These are special because they may not have a register operand to derive
the vector length from, which requires to also deal with the braodcast
case when determining vector length in build_evex_prefix().

Also drop IgnoreSize (and the now redundant size specifiers) from their
suffixed counterparts.