image: Rename load_addr, save_addr, save_size

These global variables are quite short and generic. In fact the same name
is more often used locally for struct members and function arguments.

Add a image_ prefix to make them easier to distinguish.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/nand.c

@@ -925,7 +925,7 @@ static int nand_load_image(cmd_tbl_t *cmdtp, struct mtd_info *mtd,
 
 	/* Loading ok, update default load address */
 
-	load_addr = addr;
+	image_load_addr = addr;
 
 	return bootm_maybe_autostart(cmdtp, cmd);
 }