ALSA: seq: Fix memory leak at error path in snd_seq_create_port()

We forgot to release a newly allocated item at the error path in
snd_seq_create_port().  This patch fixes it.

Fixes: 7c3f0d3d ("ALSA: seq: Check the conflicting port at port creation")
Reported-by: syzbot+cf8e7fa4eeec59b3d485@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/00000000000098ed3a0600965f89@google.com
Link: https://lore.kernel.org/r/20230717062555.31592-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/seq/seq_ports.c

@@ -149,6 +149,7 @@ int snd_seq_create_port(struct snd_seq_client *client, int port,
 	write_lock_irq(&client->ports_lock);
 	list_for_each_entry(p, &client->ports_list_head, list) {
 		if (p->addr.port == port) {
+			kfree(new_port);
 			num = -EBUSY;
 			goto unlock;
 		}