[PATCH] dmaengine: fix null ptr check for __dma_async_device_channel_register()

Add check to pointer after assignment before accessing members.

Fixes: d2fb0a043838: ("dmaengine: break out channel registration")

Reported-by: Dan Carpenter <redacted>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/dma/dmaengine.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index f3ef4edd4de1..3a62c7839861 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c

@@ -962,6 +962,9 @@ static int __dma_async_device_channel_register(struct dma_device *device,
 
 	tchan = list_first_entry_or_null(&device->channels,
 					 struct dma_chan, device_node);
+	if (!tchan)
+		return -ENODEV;
+
 	if (tchan->dev) {
 		idr_ref = tchan->dev->idr_ref;
 	} else {