dmaengine: Move kdoc description of struct dma_chan_percpu closer to it

We have split by unknown reason of kdoc and struct dma_chan_percpu definition.
Join them back. No functional change.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210518104323.37632-1-andriy.shevchenko@linux.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

include/linux/dmaengine.h

@@ -229,12 +229,6 @@ enum sum_check_flags {
  */
 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
- * @memcpy_count: transaction counter
- * @bytes_transferred: byte counter
- */
-
 /**
  * enum dma_desc_metadata_mode - per descriptor metadata mode types supported
  * @DESC_METADATA_CLIENT - the metadata buffer is allocated/provided by the
@@ -291,6 +285,11 @@ enum dma_desc_metadata_mode {
 	DESC_METADATA_ENGINE = BIT(1),
 };
 
+/**
+ * struct dma_chan_percpu - the per-CPU part of struct dma_chan
+ * @memcpy_count: transaction counter
+ * @bytes_transferred: byte counter
+ */
 struct dma_chan_percpu {
 	/* stats */
 	unsigned long memcpy_count;