[U-Boot] about to do some tidying up of the top-level README file

for an embedded linux course i'm teaching soon, i'm going to hand out an exercise to read parts of the u-boot README file and i notice there are some historical anachronisms in there i can submit patches for -- things like references to boards.cfg, and referring to a single MAINTAINERS file, that sort of thing.

i'm about to start reading and tweaking; if anyone wants to point out any other things which could be brought up to date, let me know and i can add them to the patch. no sense doing this with more than one patch.

rday