But if that's the case, it doesn't make sense to have a new vendor! If
AMD's 17h and Hygon's 18h ever diverge, you could always choose the
right behavior based on the family, without checking the vendor.
However, if the x86 maintainers prefer to have a new X86_VENDOR_*
constant, I'd just ignore the fact that AMD will skip family 18h, and
introduce vendor checks along the lines below. This has the advantage
that it's not an issue if AMD ends up _not_ skipping family 18h.