bootconfig: Fix missing return check of xbc_node_compose_key function

The function `xbc_show_list should` handle the keys during the
composition. Even the errors returned by the compose function. Instead
of removing the `ret` variable, it should save the value and show the
exact error. This missing variable is causing a compilation issue also.

Link: https://lkml.kernel.org/r/163077087861.222577.12884543474750968146.stgit@devnote2

Fixes: e5efaeb8a8 ("bootconfig: Support mixing a value and subkeys under a key")
Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/bootconfig/main.c

@@ -111,9 +111,11 @@ static void xbc_show_list(void)
 	char key[XBC_KEYLEN_MAX];
 	struct xbc_node *leaf;
 	const char *val;
+	int ret;
 
 	xbc_for_each_key_value(leaf, val) {
-		if (xbc_node_compose_key(leaf, key, XBC_KEYLEN_MAX) < 0) {
+		ret = xbc_node_compose_key(leaf, key, XBC_KEYLEN_MAX);
+		if (ret < 0) {
 			fprintf(stderr, "Failed to compose key %d\n", ret);
 			break;
 		}