dmaengine: at_xdmac: Fix missing unlock in at_xdmac_tasklet()

Add the missing unlock before return from at_xdmac_tasklet().

Fixes: e77e561 ("dmaengine: at_xdmac: Fix race over irq_status")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20220107024047.1051915-1-yangyingliang@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: Yang Yingliang

drivers/dma/at_xdmac.c

@@ -1681,8 +1681,10 @@ static void at_xdmac_tasklet(struct tasklet_struct *t)
 		__func__, atchan->irq_status);
 
 	if (!(atchan->irq_status & AT_XDMAC_CIS_LIS) &&
-	    !(atchan->irq_status & error_mask))
+	    !(atchan->irq_status & error_mask)) {
+		spin_unlock_irq(&atchan->lock);
 		return;
+	}
 
 	if (atchan->irq_status & error_mask)
 		at_xdmac_handle_error(atchan);