dmaengine: move channel device_node deletion to driver

Channel device_node deletion is managed by the device driver rather than
the dmaengine core. The deletion was accidentally introduced when making
channel unregister dynamic. It causes xilinx_dma module to crash on unload
as reported by Radhey. Remove chan->device_node delete in dmaengine and
also fix up idxd driver.

[ 42.142705] Internal error: Oops: 96000044 [#1] SMP
[ 42.147566] Modules linked in: xilinx_dma(-) clk_xlnx_clock_wizard uio_pdrv_genirq
[ 42.155139] CPU: 1 PID: 2075 Comm: rmmod Not tainted 5.10.1-00026-g3a2e6dd7a05-dirty #192
[ 42.163302] Hardware name: Enclustra XU5 SOM (DT)
[ 42.167992] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
[ 42.173996] pc : xilinx_dma_chan_remove+0x74/0xa0 [xilinx_dma]
[ 42.179815] lr : xilinx_dma_chan_remove+0x70/0xa0 [xilinx_dma]
[ 42.185636] sp : ffffffc01112bca0
[ 42.188935] x29: ffffffc01112bca0 x28: ffffff80402ea640

xilinx_dma_chan_remove+0x74/0xa0:
__list_del at ./include/linux/list.h:112 (inlined by)
__list_del_entry at./include/linux/list.h:135 (inlined by)
list_del at ./include/linux/list.h:146 (inlined by)
xilinx_dma_chan_remove at drivers/dma/xilinx/xilinx_dma.c:2546

Fixes: e81274cd6b52 ("dmaengine: add support to dynamic register/unregister of channels")
Reported-by: Radhey Shyam Pandey <[e-mail]>
Signed-off-by: Dave Jiang <[e-mail]>
Tested-by: Radhey Shyam Pandey <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>
Cc: [e-mail] # 5.9+

drivers/dma/dmaengine.c

···
 		  "%s called while %d clients hold a reference\n",
 		  __func__, chan->client_count);
 	mutex_lock(&dma_list_mutex);
-	list_del(&chan->device_node);
 	device->chancnt--;
 	chan->dev->chan = NULL;
 	mutex_unlock(&dma_list_mutex);

drivers/dma/idxd/dma.c

···
 
 void idxd_unregister_dma_channel(struct idxd_wq *wq)
 {
-	dma_async_device_channel_unregister(&wq->idxd->dma_dev, &wq->dma_chan);
+	struct dma_chan *chan = &wq->dma_chan;
+
+	dma_async_device_channel_unregister(&wq->idxd->dma_dev, chan);
+	list_del(&chan->device_node);
 }