Fix for removal of mmiowb() in linux 5.2 and above (done in spinlock_unlock now)

XDMA/linux-kernel/libxdma/libxdma.c

@@ -715,7 +715,10 @@ static struct xdma_transfer *engine_start(struct xdma_engine *engine)
 
 	dbg_tfr("ioread32(0x%p) (dummy read flushes writes).\n",
 		&engine->regs->status);
+
+#if KERNEL_VERSION(5, 1, 0) >= LINUX_VERSION_CODE
 	mmiowb();
+#endif
 
 	rv = engine_start_mode_config(engine);
 	if (rv < 0) {

XDMA/linux-kernel/xdma/cdev_xvc.c

@@ -213,7 +213,9 @@ static long xvc_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		pr_info("copy back tdo_buf failed: %d/%u.\n", rv, total_bytes);
 
 unlock:
+#if KERNEL_VERSION(5, 1, 0) >= LINUX_VERSION_CODE
 	mmiowb();
+#endif
 	spin_unlock(&xcdev->lock);
 
 cleanup: