powerpc/83xx: use ppc_6xx as arch variable for kmvect1

On this board we are using hard floating point, so select the correct
toolchain.
Signed-off-by: NHolger Brunck <holger.brunck@keymile.com>

include/configs/km/km8309-common.h

@@ -22,7 +22,7 @@
 #define CONFIG_MPC830x		1	/* MPC830x family */
 #define CONFIG_MPC8309		1	/* MPC8309 CPU specific */
 
-#define CONFIG_KM_DEF_ARCH	"arch=ppc_8xx\0"
+#define CONFIG_KM_DEF_ARCH	"arch=ppc_82xx\0"
 #define CONFIG_CMD_DIAG		1
 
 /* include common defines/options for all 83xx Keymile boards */