Input: usbtouchscreen - initialize PM mutex before using it

Mutexes shall be initialized before they are used.

Fixes: 12e510db ("Input: usbtouchscreen - fix deadlock in autosuspend")
Reported-by: syzbot+199ea16c7f26418b4365@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/usbtouchscreen.c

@@ -1659,6 +1659,8 @@ static int usbtouch_probe(struct usb_interface *intf,
 	if (!usbtouch || !input_dev)
 		goto out_free;
 
+	mutex_init(&usbtouch->pm_mutex);
+
 	type = &usbtouch_dev_info[id->driver_info];
 	usbtouch->type = type;
 	if (!type->process_pkt)