Fix typo in atmel_spi.c

Fix cut 'n paste bug in Atmel SPI driver.
Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Acked-by: David Brownell <david-b@pacbell.net>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/spi/atmel_spi.c

@@ -251,7 +251,7 @@ atmel_spi_dma_map_xfer(struct atmel_spi *as, struct spi_transfer *xfer)
 		xfer->rx_dma = dma_map_single(dev,
 				xfer->rx_buf, xfer->len,
 				DMA_FROM_DEVICE);
-		if (dma_mapping_error(xfer->tx_dma)) {
+		if (dma_mapping_error(xfer->rx_dma)) {
 			if (xfer->tx_buf)
 				dma_unmap_single(dev,
 						xfer->tx_dma, xfer->len,