dmaengine: xgene-dma: Provide descriptions for 'dev' and 'clk' in device's ddata

Fixes the following W=1 kernel build warning(s):

 drivers/dma/xgene-dma.c:310: warning: Function parameter or member 'dev' not described in 'xgene_dma'
 drivers/dma/xgene-dma.c:310: warning: Function parameter or member 'clk' not described in 'xgene_dma'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Cc: Prasad Sahu <rsahu@apm.com>
Cc: Loc Ho <lho@apm.com>
Link: https://lore.kernel.org/r/20200714111546.1755231-15-lee.jones@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/xgene-dma.c

@@ -287,6 +287,8 @@ struct xgene_dma_chan {
 
 /**
  * struct xgene_dma - internal representation of an X-Gene DMA device
+ * @dev: reference to this device's struct device
+ * @clk: reference to this device's clock
  * @err_irq: DMA error irq number
  * @ring_num: start id number for DMA ring
  * @csr_dma: base for DMA register access