[U-Boot] V2 implementation of generic distro options

[Dennis Gilmore]

In this set of patches I am adding a generic set of config options for Distros
to work with. this enables for simplified support of systems by distros. Fixed in
V2 is updating the guard to match the renamed filename since the RFC series.

I have left out any implementations in this set of patches. I am working to redo
all the implementations based on the work done by Stephen Warren in his recent set
to base on top of these and his exists work.

Dennis