virtio: don't fail on !of_device_is_compatible

A recent change checking of_device_is_compatible on probe broke some
powerpc/pseries setups. Apparently there virtio devices do not have a
"compatible" property - they are matched by PCI vendor/device ids.

Let's just skip of_node setup but proceed with initialization like we
did previously.

Fixes: 694a1116 ("virtio: Bind virtio device to device-tree node")
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio.c

@@ -345,8 +345,13 @@ static int virtio_device_of_init(struct virtio_device *dev)
 	ret = snprintf(compat, sizeof(compat), "virtio,device%x", dev->id.device);
 	BUG_ON(ret >= sizeof(compat));
 
+	/*
+	 * On powerpc/pseries virtio devices are PCI devices so PCI
+	 * vendor/device ids play the role of the "compatible" property.
+	 * Simply don't init of_node in this case.
+	 */
 	if (!of_device_is_compatible(np, compat)) {
-		ret = -EINVAL;
+		ret = 0;
 		goto out;
 	}