vexpress64: Enable VIRTIO_NET network driver

The SMSC driver is using the old driver model.

Init the virtio system in vexpress64.c so that the network device is
discovered.

Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/include/configs/vexpress_aemv8.h b/include/configs/vexpress_aemv8.h
index 5f7d19d..54e8cae 100644
--- a/include/configs/vexpress_aemv8.h
+++ b/include/configs/vexpress_aemv8.h
@@ -88,8 +88,8 @@
 #endif
 #endif /* !CONFIG_GICV3 */
 
-#ifndef CONFIG_TARGET_VEXPRESS64_JUNO
-/* The Vexpress64 simulators use SMSC91C111 */
+#if defined(CONFIG_TARGET_VEXPRESS64_BASE_FVP) && !defined(CONFIG_DM_ETH)
+/* The Vexpress64 BASE_FVP simulator uses SMSC91C111 */
 #define CONFIG_SMC91111			1
 #define CONFIG_SMC91111_BASE		(V2M_PA_BASE + 0x01A000000)
 #endif