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/mpr2.h b/include/configs/mpr2.h
index 6ebb1e1..86f6a93 100644
--- a/include/configs/mpr2.h
+++ b/include/configs/mpr2.h
@@ -27,7 +27,7 @@
 #define __MPR2_H
 
 /* Supported commands */
-#define CONFIG_CMD_ENV
+#define CONFIG_CMD_SAVEENV
 #define CONFIG_CMD_CACHE
 #define CONFIG_CMD_MEMORY
 #define CONFIG_CMD_FLASH