ti816x_evm: Change CONFIG_CMD_ASKEN to CONFIG_CMD_ASKENV

This looks like a typo. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/ti816x_evm.h b/include/configs/ti816x_evm.h
index b5af700..b7ec200 100644
--- a/include/configs/ti816x_evm.h
+++ b/include/configs/ti816x_evm.h
@@ -49,7 +49,7 @@
 
 #define CONFIG_SYS_LOAD_ADDR		0x81000000 /* Default load address */
 
-#define CONFIG_CMD_ASKEN
+#define CONFIG_CMD_ASKENV
 #define CONFIG_OMAP_GPIO
 
 #define CONFIG_FS_FAT