boards/km_arm: enable support for Macronix SPI NOR flash

The M25P80 and M25P32 SPI flashes from Numonix/Micron
will be replaced by Marconix MX25L80 and MX25L32 flashes.

Signed-off-by: Holger Brunck <holger.brunck@ch.abb.com>
CC: Stefan Roese <sr@denx.de>
CC: Valentin Longchamp <valentin.longchamp@ch.abb.com>
Reviewed-by: Stefan Roese <sr@denx.de>