Staging: hv: hv_mouse: use proper input define for bus type

The code was so close, the bus type was in a comment, so go all the way
and actually use the define here.  It's as if the original author was so
afraid of license issues if they referenced a define in the processed
code but they felt safe to keep it in a comment.  Chicken.

Cc: Hank Janssen <hjanssen@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/hv_mouse.c

@@ -922,7 +922,7 @@ static void reportdesc_callback(struct hv_device *dev, void *packet, u32 len)
 		hid_dev->ll_driver->open  = mousevsc_hid_open;
 		hid_dev->ll_driver->close = mousevsc_hid_close;
 
-		hid_dev->bus =  0x06;  /* BUS_VIRTUAL */
+		hid_dev->bus = BUS_VIRTUAL;
 		hid_dev->vendor = input_device_ctx->device_info.vendor;
 		hid_dev->product = input_device_ctx->device_info.product;
 		hid_dev->version = input_device_ctx->device_info.version;