hwtracing: intel_th: use dev_groups and not dev_attrs for bus_type

The dev_attrs field has long been "depreciated" and is finally being
removed, and as this driver isn't even using it, just drop the NULL
setting, it is pointless.

Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/intel_th/core.c

@@ -139,7 +139,6 @@ static int intel_th_remove(struct device *dev)
 
 static struct bus_type intel_th_bus = {
 	.name		= "intel_th",
-	.dev_attrs	= NULL,
 	.match		= intel_th_match,
 	.probe		= intel_th_probe,
 	.remove		= intel_th_remove,