sunrpc: clear XPRT_SOCK_UPD_TIMEOUT when reset transport

In the Linux kernel, the following vulnerability has been resolved: sunrpc: clear XPRT_SOCK_UPD_TIMEOUT when reset transport Since transport->sock has been set to NULL during reset transport, XPRT_SOCK_UPD_TIMEOUT also needs to be cleared. Otherwise, the xs_tcp_set_socket_timeouts() may be triggered in xs_tcp_send_request() to dereference the transport->sock that has been set to NULL.