dmaengine: make clients responsible for managing channels

The current implementation assumes that a channel will only be used by one
client at a time.  In order to enable channel sharing the dmaengine core is
changed to a model where clients subscribe to channel-available-events.
Instead of tracking how many channels a client wants and how many it has
received the core just broadcasts the available channels and lets the
clients optionally take a reference.  The core learns about the clients'
needs at dma_event_callback time.

In support of multiple operation types, clients can specify a capability
mask to only be notified of channels that satisfy a certain set of
capabilities.

Changelog:
* removed DMA_TX_ARRAY_INIT, no longer needed
* dma_client_chan_free -> dma_chan_release: switch to global reference
  counting only at device unregistration time, before it was also happening
  at client unregistration time
* clients now return dma_state_client to dmaengine (ack, dup, nak)
* checkpatch.pl fixes
* fixup merge with git-ioat

Cc: Chris Leech <christopher.leech@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: David S. Miller <davem@davemloft.net>

drivers/dma/ioatdma.c

@@ -72,7 +72,6 @@ static int enumerate_dma_channels(struct ioat_device *device)
 		INIT_LIST_HEAD(&ioat_chan->used_desc);
 		/* This should be made common somewhere in dmaengine.c */
 		ioat_chan->common.device = &device->common;
-		ioat_chan->common.client = NULL;
 		list_add_tail(&ioat_chan->common.device_node,
 		              &device->common.channels);
 	}