soc: mediatek: knows_txdone needs to be set in Mediatek CMDQ helper

Mediatek CMDQ driver have a mechanism to do TXDONE_BY_ACK,
so we should set knows_txdone.

Fixes:576f1b4b ("soc: mediatek: Add Mediatek CMDQ helper")

Cc: stable@vger.kernel.org # v5.0+
Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>

drivers/soc/mediatek/mtk-cmdq-helper.c

@@ -78,6 +78,7 @@ struct cmdq_client *cmdq_mbox_create(struct device *dev, int index, u32 timeout)
 	client->pkt_cnt = 0;
 	client->client.dev = dev;
 	client->client.tx_block = false;
+	client->client.knows_txdone = true;
 	client->chan = mbox_request_channel(&client->client, index);
 
 	if (IS_ERR(client->chan)) {