tier classifications: mips listed as 2 in one place and 3 in another

[Rodney W. Grimes]

> 
> https://www.freebsd.org/platforms/ classifies mips as tier 3.
> 
> https://www.freebsd.org/doc/en_US.ISO8859-1/articles/committers-guide/archs.html classifies
> mips as tier 2.
> 

There is also tier information appearing in:
http://pkg.freebsd.org/
and probably other places if we dig around

> They agree for:
> 
> Tier 1: amd64, i386
> 
> Tier 2: arm64, arm, powerpc, sparc64
> 
> Tier 3: risc-v
> 
> 
> (I noticed this while checking if the official status had changed for
> arm64 or arm.)

The tier information should be refactored to a single document and
other places set up as pointers to that document, or some mechanism
to have documents extract that information from a central single
place of truth.

Further note that the package system treats powerpc vs powerpc64
differently (no packages for powerpc).

-- 
Rod Grimes                                                 rgrimes at freebsd.org