arm/km: use board KM_ENV_BUS for CONFIG_I2C_ENV_EEPROM_BUS

This is defined for all km_kirkwood boards and was not used up to now.
This value was the same for all boards but it could be changed for some
boards (and thus needs to be defined for every board).

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>
cc: Heiko Schocher <hs@denx.de>

include/configs/km/km_arm.h

@@ -208,7 +208,7 @@ int get_scl(void);
 #define CONFIG_SYS_EEPROM_WREN
 #define CONFIG_ENV_OFFSET		0x0 /* no bracets! */
 #define CONFIG_ENV_SIZE			(0x2000 - CONFIG_ENV_OFFSET)
-#define CONFIG_I2C_ENV_EEPROM_BUS	"pca9547:70:d\0"
+#define CONFIG_I2C_ENV_EEPROM_BUS	KM_ENV_BUS "\0"
 
 /* offset redund: (CONFIG_ENV_OFFSET + CONFIG_ENV_SIZE) */
 #define CONFIG_SYS_REDUNDAND_ENVIRONMENT