dmaengine: sun6i: Free the interrupt before killing the tasklet

There's still a small window between the call to sun6i_kill_tasklet and the end
of the driver remove function where a spurious interrupt might trigger, and
start using deallocated resources.

Replace the call to synchronize_irq by a free_irq, so that we're sure that we
won't get any further interrupts when we're deallocating resources.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/sun6i-dma.c

@@ -836,8 +836,8 @@ static inline void sun6i_kill_tasklet(struct sun6i_dma_dev *sdev)
 	/* Prevent spurious interrupts from scheduling the tasklet */
 	atomic_inc(&sdev->tasklet_shutdown);
 
-	/* Make sure all interrupts are handled */
-	synchronize_irq(sdev->irq);
+	/* Make sure we won't have any further interrupts */
+	devm_free_irq(sdev->slave.dev, sdev->irq, sdev);
 
 	/* Actually prevent the tasklet from being scheduled */
 	tasklet_kill(&sdev->task);