I/OAT: clean up of dca provider start and stop

Don't start ioat_dca if ioat_dma didn't start, and then stop ioat_dca
before stopping ioat_dma.  Since the ioat_dma side does the pci device
work, This takes care of ioat_dca trying to use a bad device reference.

Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/dma/ioat_dma.c b/drivers/dma/ioat_dma.c
index 59d4344..725f83f 100644
--- a/drivers/dma/ioat_dma.c
+++ b/drivers/dma/ioat_dma.c
@@ -941,10 +941,10 @@
 	struct dma_chan *chan, *_chan;
 	struct ioat_dma_chan *ioat_chan;
 
-	dma_async_device_unregister(&device->common);
-
 	ioat_dma_remove_interrupts(device);
 
+	dma_async_device_unregister(&device->common);
+
 	pci_pool_destroy(device->dma_pool);
 	pci_pool_destroy(device->completion_pool);