Fix file descriptor that is passed to io_uring_register_eventfd()

Fix Change-Id I03752c0114cc6fad0c31fff6fff43072f36a50a7

Change-Id: Ie085c7cb3eb57e0da10485be8f90208cb41b0073
diff --git a/src/core/osmo_io_uring.c b/src/core/osmo_io_uring.c
index e163ee0..569f150 100644
--- a/src/core/osmo_io_uring.c
+++ b/src/core/osmo_io_uring.c
@@ -108,7 +108,7 @@
 		io_uring_queue_exit(&g_ring.ring);
 		osmo_panic("failure registering io_uring-eventfd as osmo_fd: %d\n", rc);
 	}
-	rc = io_uring_register_eventfd(&g_ring.ring, rc);
+	rc = io_uring_register_eventfd(&g_ring.ring, evfd);
 	if (rc < 0) {
 		osmo_fd_unregister(&g_ring.event_ofd);
 		close(evfd);