dmaengine: pch_dma: use tasklet_kill in teardown

As discussed in [1] the tasklet_disable is not a proper function for teardown.
We need to ensure irq is disabled, followed by ensuring that don't schedule any
more tasklets and then its safe to use tasklet_kill().

Here in pch dma driver we need to use free_irq() before tasklet_kill(). So move
up the free_irq() which will ensure that the irq is disabled and also wait till
all scheduled interrupts are executed by invoking synchronize_irq().

[1]: http://lwn.net/Articles/588457/Reported-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NVinod Koul <vinod.koul@intel.com>

drivers/dma/pch_dma.c

@@ -964,16 +964,16 @@ static void pch_dma_remove(struct pci_dev *pdev)
 	if (pd) {
 		dma_async_device_unregister(&pd->dma);
 
+		free_irq(pdev->irq, pd);
+
 		list_for_each_entry_safe(chan, _c, &pd->dma.channels,
 					 device_node) {
 			pd_chan = to_pd_chan(chan);
 
-			tasklet_disable(&pd_chan->tasklet);
 			tasklet_kill(&pd_chan->tasklet);
 		}
 
 		pci_pool_destroy(pd->pool);
-		free_irq(pdev->irq, pd);
 		pci_iounmap(pdev, pd->membase);
 		pci_release_regions(pdev);
 		pci_disable_device(pdev);