mx51evk: Allow booting a zImage kernel

Allow booting a zImage kernel.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/include/configs/mx51evk.h b/include/configs/mx51evk.h
index d3edcba..8cf59fe 100644
--- a/include/configs/mx51evk.h
+++ b/include/configs/mx51evk.h
@@ -144,7 +144,7 @@
  ***********************************************************/
 
 #include <config_cmd_default.h>
-
+#define CONFIG_CMD_BOOTZ
 #undef CONFIG_CMD_IMLS
 
 #define CONFIG_CMD_DATE