KM: fix typo in default environment

The ip kernel parameter had a typo in it (we've been lucky that it has
worked until now).
Signed-off-by: NValentin Longchamp <valentin.longchamp@keymile.com>

include/configs/km/keymile-common.h

@@ -165,7 +165,7 @@
 	"add_default="							\
 		"setenv bootargs ${bootargs} "				\
 		"ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}"	\
-		":${hostname}:${netdev}:off3"				\
+		":${hostname}:${netdev}:off:"				\
 		" console=" CONFIG_KM_CONSOLE_TTY ",${baudrate}"	\
 		" mem=${kernelmem} init=${init}"			\
 		CONFIG_KM_ECC_MODE					\