HID: hid-picolcd: don't use flush_scheduled_work()

flush_scheduled_work() is deprecated and scheduled to be removed.
Directly flush picolcd_fb_cleanup on exit instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-picolcd.c

@@ -2750,7 +2750,7 @@ static void __exit picolcd_exit(void)
 {
 	hid_unregister_driver(&picolcd_driver);
 #ifdef CONFIG_HID_PICOLCD_FB
-	flush_scheduled_work();
+	flush_work_sync(&picolcd_fb_cleanup);
 	WARN_ON(fb_pending);
 #endif
 }