HID: remove no longer used hid->open field

Now that all users have migrated to use hid->ll_open_count, we can remove
hid->open field.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

include/linux/hid.h

@@ -548,7 +548,6 @@ struct hid_device {							/* device report descriptor */
 	void *hiddev;							/* The hiddev structure */
 	void *hidraw;
 
-	int open;							/* is the device open by anyone? */
 	char name[128];							/* Device name */
 	char phys[64];							/* Device physical location */
 	char uniq[64];							/* Device unique identifier (serial #) */