[infiniband] Use a one-shot process for CMRC shutdown

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/infiniband/ib_cmrc.c

 	ib_destroy_cq ( cmrc->ibdev, cmrc->cq );
 	ib_close ( cmrc->ibdev );
 
-	/* Remove process from run queue */
-	process_del ( &cmrc->shutdown );
-
 	/* Drop the remaining reference */
 	ref_put ( &cmrc->refcnt );
 }
 
 /** CMRC shutdown process descriptor */
 static struct process_descriptor ib_cmrc_shutdown_desc =
-	PROC_DESC ( struct ib_cmrc_connection, shutdown, ib_cmrc_shutdown );
+	PROC_DESC_ONCE ( struct ib_cmrc_connection, shutdown,
+			 ib_cmrc_shutdown );
 
 /**
  * Open CMRC connection