tools/bootconfig: Fix apply_xbc() to return zero on success

The return of apply_xbc() returns the result of the last write() call, which
is not what is expected. It should only return zero on success.

Link: https://lore.kernel.org/r/20200508093059.GF9365@kadam

Fixes: 8842604 ("tools/bootconfig: Fix resource leak in apply_xbc()")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/bootconfig/main.c

@@ -337,6 +337,7 @@ int apply_xbc(const char *path, const char *xbc_path)
 		pr_err("Failed to apply a boot config magic: %d\n", ret);
 		goto out;
 	}
+	ret = 0;
 out:
 	close(fd);
 	free(data);