CVE-2026-89531: svcrdma: Reject connection when transport allocation fails

In the Linux kernel, the following vulnerability has been resolved: svcrdma: Reject connection when transport allocation fails handle_connect_req() returns without action when svc_rdma_create_xprt() fails to allocate the new transport. The CM core returns 0 for CONNECT_REQUEST events, so it does not destroy the new rdma_cm_id. Each allocation failure under memory pressure leaks one rdma_cm_id, and a remote peer driving connection attempts can amplify this. Reject the connection by returning a non-zero status from the CM event handler, which tells the CM core to destroy the orphaned cm_id.