x86: fold AddrPrefixOpReg templates

There's no need to have separate Cpu64 and CpuNo64 templates: There
already is special logic handling the attribute, and all that's needed
is rejecting 16-bit address registers in 64-bit mode. Suppress suffix
guessing and group all involved logic together, outside of suffix
processing (arguably it doesn't even belong in process_suffix()).

Also, since no AddrPrefixOpReg template permits any suffixes, move the
No_*Suf specifiers for them to a central place. Along with this drop
the no longer relevant NoRex64 from there.