rename CONFIG_CMD_ENV to CONFIG_CMD_SAVEENV

The CONFIG_CMD_ENV option controls enablement of the `saveenv` command
rather than a generic "env" command, or anything else related to the
environment.  So, let's make sure the define is named accordingly.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/configs/cm4008.h b/include/configs/cm4008.h
index cfe6de7..ce36a24 100644
--- a/include/configs/cm4008.h
+++ b/include/configs/cm4008.h
@@ -73,7 +73,7 @@
  */
 #include <config_cmd_default.h>
 
-#undef CONFIG_CMD_ENV
+#undef CONFIG_CMD_SAVEENV
 
 
 #define CONFIG_BOOTDELAY	0