[U-Boot] MAINTAINERS sorting order

Hello Wolfgang,

just as I was checking who was maintainer for at91rm9200ek, I noticed that under the respective architecture sections there are sometimes boards that belong to another architecture. Even my new patch for top9000 would put that line into the PPC section. Heiko e.g. has an ARM board there as well. But there are also PPC boards in the ARM section.

I think a strict adherence to that sectionalism would in some cases cause the same maintainer to appear multiple times. How is the preferred way? Maybe in the future drop that sectionalism altogether?

Best Regards, Reinhard