uboot-phytec

arm/km: cleanup km_kirkwood boards

Remove config options from boards.cfg and simply add one switch
per board and differ afterwards in km_kirkwood.h between the features.
More boards are upcoming and therefore it's easier to have this
at one place.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Gerlando Falauto <gerlando.falauto@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>