cpuid.4: Note which CPUs don't support CPUID and what happens

cpuid.4: Note which CPUs don't support CPUID and what happens

"Early 486" comes from an uncited wikipedia table, added in
<https://en.wikipedia.org/w/index.php?title=CPUID&diff=prev&oldid=592047209>
<https://en.wikipedia.org/w/index.php?title=CPUID&diff=prev&oldid=592047978>
but I spot-checked the rest of the table accurate to CPUs in my house
(the oldest of which is an original Celeron, so no 486),
and "early 486" is better than "early x86" which can mean anything.

This does leave earlier x86 unmentioned,
but Linux hasn't targeted those in over a decade,
so they're out of scope anyway.

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx@kernel.org>