spi: atmel: trivial: remove unused fields in DMA structure

The atmel_spi_dma structure was cluttered with unused fields relative
to older DMA channel selection API. Remove them.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-atmel.c

@@ -268,10 +268,6 @@
 struct atmel_spi_dma {
 	struct dma_chan			*chan_rx;
 	struct dma_chan			*chan_tx;
-	struct dma_async_tx_descriptor	*data_desc_rx;
-	struct dma_async_tx_descriptor	*data_desc_tx;
-
-	struct at_dma_slave	dma_slave;
 };
 
 struct atmel_spi_caps {