km: remove obsolete definitions in KM header files

After moving the KM specific configurations to Kconfig, the associated
preprocessor definitions can now be removed in the headers. Moreover, the
whitelist has been adapted correspondingly.

Signed-off-by: Pascal Linder <pascal.linder@edu.hefr.ch>
Signed-off-by: Holger Brunck <holger.brunck@ch.abb.com>
Signed-off-by: Stefan Roese <sr@denx.de>