linux/dmaengine.h: fix a few kernel-doc warnings

The comment block for "Interleaved Transfer Request" should not begin
with "/**" since it is not in kernel-doc format.

Fix doc name for enum sum_check_flags.

Fix all (4) missing struct member warnings.

Use "Warning:" for one "Note:" in enum dma_desc_metadata_mode since
scripts/kernel-doc does not allow more than one Note:
per function or identifier description.

This leaves around 49 kernel-doc warnings like:
include/linux/dmaengine.h:43: warning: Enum value 'DMA_OUT_OF_ORDER' not described in enum 'dma_status'

and another scripts/kernel-doc problem with it not being able to parse
some typedefs.

Fixes: b14dab792dee ("DMAEngine: Define interleaved transfer request api")
Fixes: ad283ea4a3ce ("async_tx: add sum check flags")
Fixes: 272420214d26 ("dmaengine: Add DMA_CTRL_REUSE")
Fixes: f067025bc676 ("dmaengine: add support to provide error result from a DMA transation")
Fixes: d38a8c622a1b ("dmaengine: prepare for generic 'unmap' data")
Fixes: 5878853fc938 ("dmaengine: Add API function dmaengine_prep_peripheral_dma_vec()")
Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Dave Jiang <[e-mail]>
Cc: Paul Cercueil <[e-mail]>
Cc: Nuno Sa <[e-mail]>
Cc: Vinod Koul <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

include/linux/dmaengine.h

···
 	DMA_TRANS_NONE,
 };
 
-/**
+/*
  * Interleaved Transfer Request
  * ----------------------------
  * A chunk is collection of contiguous bytes to be transferred.
···
 };
 
 /**
- * enum pq_check_flags - result of async_{xor,pq}_zero_sum operations
+ * enum sum_check_flags - result of async_{xor,pq}_zero_sum operations
  * @SUM_CHECK_P_RESULT - 1 if xor zero sum error, 0 otherwise
  * @SUM_CHECK_Q_RESULT - 1 if reed-solomon zero sum error, 0 otherwise
  */
···
  *	pointer to the engine's metadata area
  *   4. Read out the metadata from the pointer
  *
- * Note: the two mode is not compatible and clients must use one mode for a
+ * Warning: the two modes are not compatible and clients must use one mode for a
  * descriptor.
  */
 enum dma_desc_metadata_mode {
···
  * @phys: physical address of the descriptor
  * @chan: target channel for this operation
  * @tx_submit: accept the descriptor, assign ordered cookie and mark the
+ * @desc_free: driver's callback function to free a resusable descriptor
+ *	after completion
  * descriptor pending. To be pushed on .issue_pending() call
  * @callback: routine to call after this operation is complete
+ * @callback_result: error result from a DMA transaction
  * @callback_param: general parameter to pass to the callback routine
+ * @unmap: hook for generic DMA unmap data
  * @desc_metadata_mode: core managed metadata mode to protect mixed use of
  *	DESC_METADATA_CLIENT or DESC_METADATA_ENGINE. Otherwise
  *	DESC_METADATA_NONE
···
  * @device_prep_dma_memset: prepares a memset operation
  * @device_prep_dma_memset_sg: prepares a memset operation over a scatter list
  * @device_prep_dma_interrupt: prepares an end of chain interrupt operation
+ * @device_prep_peripheral_dma_vec: prepares a scatter-gather DMA transfer,
+ *	where the address and size of each segment is located in one entry of
+ *	the dma_vec array.
  * @device_prep_slave_sg: prepares a slave dma operation
  * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for audio.
  *	The function takes a buffer of size buf_len. The callback function will