Staging: hv: mousevsc: Properly add the hid device

We need to properly add the hid device to correctly initialize the
sysfs state. While this patch is against the staging tree; Jiri,
please pick up this patch as you merge the Hyper-V mouse driver.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reported-by: Fuzhou Chen <fuzhouch@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/hv_mouse.c

@@ -519,6 +519,10 @@ static int mousevsc_probe(struct hv_device *device,
 
 	sprintf(hid_dev->name, "%s", "Microsoft Vmbus HID-compliant Mouse");
 
+	ret = hid_add_device(hid_dev);
+	if (ret)
+		goto probe_err1;
+
 	ret = hid_parse_report(hid_dev, input_dev->report_desc,
 				input_dev->report_desc_size);