[coreboot] Revert socket abstraction change

[Myles Watson]

I agree that it's dangerous because it's not abstracted correctly yet.
 I'm not sure what the right fix is, but I don't think there should be
this much duplication in every socket Makefile.inc.

Maybe the best thing would be for someone to take a socket that
supports two families and implement it for Kconfig so that we can see
what shakes out.

Signed-off-by: Myles Watson

Thanks,
Myles