dmaengine: stm32-dma: clean channel configuration when channel is freed

When dma_channel_release is called, it means that the channel won't be used
anymore with the configuration it had. To ensure a future client can safely
use the channel after it has been released, clean the configuration done
when channel was requested.

Signed-off-by: Amelie Delaunay <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/stm32-dma.c

···
 	pm_runtime_put(dmadev->ddev.dev);
 
 	vchan_free_chan_resources(to_virt_chan(c));
+	stm32_dma_clear_reg(&chan->chan_reg);
+	chan->threshold = 0;
 }
 
 static void stm32_dma_desc_free(struct virt_dma_desc *vdesc)