HID: i2c_hid: enable i2c-hid devices to suspend/resume asynchronously

i2c-hid devices' suspend/resume are usually time-consuming process.
For example, the touch controller(i2c-ATML1000:00) on ASUS T100 tablet
takes about 160ms for suspending and 120ms for resuming. This patch
enables i2c-hid devices to suspend/resume asynchronously. This will
take advantage of multicore and speed up system suspend/resume process.
Signed-off-by: Zhonghui Fu <zhonghui.fu@linux.intel.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/i2c-hid/i2c-hid.c

@@ -1020,6 +1020,7 @@ static int i2c_hid_probe(struct i2c_client *client,
 	pm_runtime_get_noresume(&client->dev);
 	pm_runtime_set_active(&client->dev);
 	pm_runtime_enable(&client->dev);
+	device_enable_async_suspend(&client->dev);
 
 	ret = i2c_hid_fetch_hid_descriptor(ihid);
 	if (ret < 0)