Sync io_uring.h header with 5.6 kernel bits
Just IOSQE_ASYNC was missing.
@@ -51,6 +51,7 @@ struct io_uring_sqe {
#define IOSQE_IO_DRAIN (1U << 1) /* issue after inflight IO */
#define IOSQE_IO_LINK (1U << 2) /* links next sqe */
#define IOSQE_IO_HARDLINK (1U << 3) /* like LINK, but stronger */
+#define IOSQE_ASYNC (1U << 4) /* always go async */
/*
* io_uring_setup() flags
