A race possibility exists if a DMA slave driver tries to free channel
resources witout waiting for all transfers to complete and without
explicitly terminating all requests. In such a case the IRQ processing
thread can race with .device_free_chan_resources(). To fix this race empty
all descriptor lists before freeing descriptor cache.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: NVinod Koul <vinod.koul@intel.com>