Start the channel tear down only if the channel is busy, else just
bail out. In some cases its seen that by the time the tear down is
initiated the cppi completes the DMA, especially in ISOCH transfers.
Signed-off-by: NGeorge Cherian <george.cherian@ti.com>
Signed-off-by: NVinod Koul <vinod.koul@intel.com>