Initial support for MT7620

[Adrian Chadd]

Ok, there's a lot of new work in this patch you sent me. It'd have to
be broken into smaller pieces.

So yeah, I may end up doing the temporary stuff as part of this work,
because it'll at least make it easier to add more derivative chipsets.
I also have the intrng mips stuff from kan@ to intergrate into -head.

Can you poke the patch author to see if they're willing to work with
us to break this patchset out into smaller pieces?



-adrian