uio_hv_generic: make ring buffer attribute for primary channel

The primary channel also needs a ring buffer attribute. This allows
application to check if kernel supports uio sub channels, and also
makes all channels use consistent API.

Fixes: 37b96a4931db ("uio_hv_generic: support sub-channels")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio_hv_generic.c

@@ -326,6 +326,11 @@ hv_uio_probe(struct hv_device *dev,
 	vmbus_set_chn_rescind_callback(dev->channel, hv_uio_rescind);
 	vmbus_set_sc_create_callback(dev->channel, hv_uio_new_channel);
 
+	ret = sysfs_create_bin_file(&dev->channel->kobj, &ring_buffer_bin_attr);
+	if (ret)
+		dev_notice(&dev->device,
+			   "sysfs create ring bin file failed; %d\n", ret);
+
 	hv_set_drvdata(dev, pdata);
 
 	return 0;