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>

README

diff --git a/README b/README
index b23a512..b64c159 100644
--- a/README
+++ b/README
@@ -608,7 +608,7 @@
 		CONFIG_CMD_ECHO		  echo arguments
 		CONFIG_CMD_EEPROM	* EEPROM read/write support
 		CONFIG_CMD_ELF		* bootelf, bootvx
-		CONFIG_CMD_ENV		  saveenv
+		CONFIG_CMD_SAVEENV	  saveenv
 		CONFIG_CMD_FDC		* Floppy Disk Support
 		CONFIG_CMD_FAT		* FAT partition support
 		CONFIG_CMD_FDOS		* Dos diskette Support