dmaengine: at_hdmac: fix device leak on of_dma_xlate()

Make sure to drop the reference taken when looking up the DMA platform
device during of_dma_xlate() when releasing channel resources.

Note that commit 3832b78 ("dmaengine: at_hdmac: add missing
put_device() call in at_dma_xlate()") fixed the leak in a couple of
error paths but the reference is still leaking on successful allocation.

Fixes: bbe89c8 ("at_hdmac: move to generic DMA binding")
Fixes: 3832b78 ("dmaengine: at_hdmac: add missing put_device() call in at_dma_xlate()")
Cc: stable@vger.kernel.org	# 3.10: 3832b78
Cc: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20251117161258.10679-2-johan@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: jhovold

drivers/dma/at_hdmac.c

@@ -1765,6 +1765,7 @@ static int atc_alloc_chan_resources(struct dma_chan *chan)
 static void atc_free_chan_resources(struct dma_chan *chan)
 {
 	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
+	struct at_dma_slave	*atslave;
 
 	BUG_ON(atc_chan_is_enabled(atchan));
 
@@ -1774,8 +1775,12 @@ static void atc_free_chan_resources(struct dma_chan *chan)
 	/*
 	 * Free atslave allocated in at_dma_xlate()
 	 */
-	kfree(chan->private);
-	chan->private = NULL;
+	atslave = chan->private;
+	if (atslave) {
+		put_device(atslave->dma_dev);
+		kfree(atslave);
+		chan->private = NULL;
+	}
 
 	dev_vdbg(chan2dev(chan), "free_chan_resources: done\n");
 }