expo: Destroy the cedit expo when done

Once 'cedit run' is completed, destroy the expo so that a fresh one is
used for any future editing.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/cedit.c b/cmd/cedit.c
index f696356..20f48ae 100644
--- a/cmd/cedit.c
+++ b/cmd/cedit.c
@@ -287,6 +287,8 @@
 		log_err("Failed (err=%dE)\n", ret);
 		return CMD_RET_FAILURE;
 	}
+	expo_destroy(cur_exp);
+	cur_exp = NULL;
 
 	return 0;
 }