dmaengine: update kerneldoc

Some of the kerneldoc comments in the dmaengine header describe
already removed structure members.  Remove them.

Also add a short description for dma_device->device_is_tx_complete.
Signed-off-by: NJohannes Weiner <jw@emlix.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

include/linux/dmaengine.h

@@ -97,7 +97,6 @@ typedef struct { DECLARE_BITMAP(bits, DMA_TX_TYPE_END); } dma_cap_mask_t;
 
 /**
  * struct dma_chan_percpu - the per-CPU part of struct dma_chan
- * @refcount: local_t used for open-coded "bigref" counting
  * @memcpy_count: transaction counter
  * @bytes_transferred: byte counter
  */
@@ -114,9 +113,6 @@ struct dma_chan_percpu {
  * @cookie: last cookie value returned to client
  * @chan_id: channel ID for sysfs
  * @dev: class device for sysfs
- * @refcount: kref, used in "bigref" slow-mode
- * @slow_ref: indicates that the DMA channel is free
- * @rcu: the DMA channel's RCU head
  * @device_node: used to add this to the device chan list
  * @local: per-cpu pointer to a struct dma_chan_percpu
  * @client-count: how many clients are using this channel
@@ -211,8 +207,6 @@ struct dma_async_tx_descriptor {
  * @global_node: list_head for global dma_device_list
  * @cap_mask: one or more dma_capability flags
  * @max_xor: maximum number of xor sources, 0 if no capability
- * @refcount: reference count
- * @done: IO completion struct
  * @dev_id: unique device ID
  * @dev: struct device reference for dma mapping api
  * @device_alloc_chan_resources: allocate resources and return the
@@ -225,6 +219,7 @@ struct dma_async_tx_descriptor {
  * @device_prep_dma_interrupt: prepares an end of chain interrupt operation
  * @device_prep_slave_sg: prepares a slave dma operation
  * @device_terminate_all: terminate all pending operations
+ * @device_is_tx_complete: poll for transaction completion
  * @device_issue_pending: push pending transactions to hardware
  */
 struct dma_device {