USB: oxu210hp: release spinlock on error path

Smatch complained about this missing spinlock.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/oxu210hp-hcd.c

@@ -660,13 +660,13 @@ static struct ehci_qh *oxu_qh_alloc(struct oxu_hcd *oxu)
 		if (qh->dummy == NULL) {
 			oxu_dbg(oxu, "no dummy td\n");
 			oxu->qh_used[i] = 0;
-
-			return NULL;
+			qh = NULL;
+			goto unlock;
 		}
 
 		oxu->qh_used[i] = 1;
 	}
-
+unlock:
 	spin_unlock(&oxu->mem_lock);
 
 	return qh;