hvsi: don't use flush_scheduled_work()

flush_scheduled_work() is deprecated and scheduled to be removed.
Directly cancel hp->writer and flush hp->handshaker instead.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>

drivers/char/hvsi.c

@@ -850,8 +850,8 @@ static void hvsi_flush_output(struct hvsi_struct *hp)
 	wait_event_timeout(hp->emptyq, (hp->n_outbuf <= 0), HVSI_TIMEOUT);
 
 	/* 'writer' could still be pending if it didn't see n_outbuf = 0 yet */
-	cancel_delayed_work(&hp->writer);
-	flush_scheduled_work();
+	cancel_delayed_work_sync(&hp->writer);
+	flush_work_sync(&hp->handshaker);
 
 	/*
 	 * it's also possible that our timeout expired and hvsi_write_worker