dmaengine: tegra-apb: Prevent race conditions on channel's freeing

[ Upstream commit 8e84172e ]

It's incorrect to check the channel's "busy" state without taking a lock.
That shouldn't cause any real troubles, nevertheless it's always better
not to have any race conditions in the code.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20200209163356.6439-5-digetx@gmail.comSigned-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/dma/tegra20-apb-dma.c

@@ -1225,7 +1225,6 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
 
 	dev_dbg(tdc2dev(tdc), "Freeing channel %d\n", tdc->id);
 
-	if (tdc->busy)
 	tegra_dma_terminate_all(dc);
 
 	spin_lock_irqsave(&tdc->lock, flags);