[System-dt] Don't ever add one to #address-cells

Stefano,

If we do need ranges, regs, and address-maps to contain a "address space" identifier, then I purpose a #space-cells value.  Expected values are 1 or 0 and assumed to be 0 where not specified. I think this resolves the ambiguity of meaning in address-cells between normal DT and system DT.

I am sure it is a bigger change to the tools and spec but adding 1 to address cells just seems like a hack.

Thanks, Bill