dmaengine: at_hdmac: remove some at_dma_slave comments

These comments were covering removed struct at_dma_slave fields.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

arch/arm/mach-at91/include/mach/at_hdmac.h

@@ -26,11 +26,6 @@ struct at_dma_platform_data {
 /**
  * struct at_dma_slave - Controller-specific information about a slave
  * @dma_dev: required DMA master device
- * @tx_reg: physical address of data register used for
- *	memory-to-peripheral transfers
- * @rx_reg: physical address of data register used for
- *	peripheral-to-memory transfers
- * @reg_width: peripheral register width
  * @cfg: Platform-specific initializer for the CFG register
  * @ctrla: Platform-specific initializer for the CTRLA register
  */