mvebu: split base-files across subtargets

mvebu: split base-files across subtargets

For the mvebu target in particular, there is a lot of files in
base-files that are only relevant for one subtarget. Improve
overview and reduce size per subtarget by moving/splitting
base-files depending on the subtarget they belong to.

While at it, consolidate 01_leds by using the model part of
the board name as variable.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Acked-by: Tomasz Maciej Nowak <tomek_n@o2.pl>