xilinx.h: Error check when setting links

Assert that the ethernet and dma controller are sucessfully linked to their
peers.

Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>

hw/xilinx.h

diff --git a/hw/xilinx.h b/hw/xilinx.h
index 45a6bdc..4d29265 100644
--- a/hw/xilinx.h
+++ b/hw/xilinx.h
@@ -55,13 +55,16 @@
                           int txmem, int rxmem)
 {
     DeviceState *dev;
+    Error *errp = NULL;
+
     qemu_check_nic_model(nd, "xlnx.axi-ethernet");
 
     dev = qdev_create(NULL, "xlnx.axi-ethernet");
     qdev_set_nic_properties(dev, nd);
     qdev_prop_set_uint32(dev, "rxmem", rxmem);
     qdev_prop_set_uint32(dev, "txmem", txmem);
-    object_property_set_link(OBJECT(dev), OBJECT(peer), "tx_dev", NULL);
+    object_property_set_link(OBJECT(dev), OBJECT(peer), "tx_dev", &errp);
+    assert_no_error(errp);
     qdev_init_nofail(dev);
     sysbus_mmio_map(sysbus_from_qdev(dev), 0, base);
     sysbus_connect_irq(sysbus_from_qdev(dev), 0, irq);
@@ -74,8 +77,11 @@
                            target_phys_addr_t base, qemu_irq irq,
                            qemu_irq irq2, int freqhz)
 {
+    Error *errp = NULL;
+
     qdev_prop_set_uint32(dev, "freqhz", freqhz);
-    object_property_set_link(OBJECT(dev), OBJECT(peer), "tx_dev", NULL);
+    object_property_set_link(OBJECT(dev), OBJECT(peer), "tx_dev", &errp);
+    assert_no_error(errp);
     qdev_init_nofail(dev);
 
     sysbus_mmio_map(sysbus_from_qdev(dev), 0, base);