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/m501sk.h b/include/configs/m501sk.h
index eab37df..a432850 100644
--- a/include/configs/m501sk.h
+++ b/include/configs/m501sk.h
@@ -154,7 +154,7 @@
 #define CONFIG_CMD_IMI
 #define CONFIG_CMD_NFS
 #define CONFIG_CMD_FLASH
-#define CONFIG_CMD_ENV
+#define CONFIG_CMD_SAVEENV
 
 #define CONFIG_SYS_HUSH_PARSER
 #define CONFIG_AUTO_COMPLETE