net/9p: clarify trans_fd parse_opt failure handling

This parse_opts will set invalid opts.rfd/wfd in case of failure which
we already check, but it is not clear for readers that parse_opts error
are handled in p9_fd_create: clarify this by explicitely checking the
return value.

Link: https://lkml.kernel.org/r/20220921210921.1654735-1-floridsleeves@gmail.com
Signed-off-by: Li Zhong <floridsleeves@gmail.com>
[Dominique: reworded commit message to clarify this is NOOP]
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Author: FloridSleeves

net/9p/trans_fd.c

@@ -1074,7 +1074,9 @@ p9_fd_create(struct p9_client *client, const char *addr, char *args)
 	int err;
 	struct p9_fd_opts opts;
 
-	parse_opts(args, &opts);
+	err = parse_opts(args, &opts);
+	if (err < 0)
+		return err;
 	client->trans_opts.fd.rfd = opts.rfd;
 	client->trans_opts.fd.wfd = opts.wfd;