spi: s3c64xx: Zero dma_slave_config struct in prepare_dma()

Not all fields of dma_slave_config struct are being initialized by
prepare_dma() function, leaving those which are not in undefined state,
which can confuse DMA drivers using them.

This patch adds call to memset() to zero the struct before initializing
a subset of its fields.
Signed-off-by: NTomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

drivers/spi/spi-s3c64xx.c

@@ -392,6 +392,8 @@ static void prepare_dma(struct s3c64xx_spi_dma_data *dma,
 	struct scatterlist sg;
 	struct dma_async_tx_descriptor *desc;
 
+	memset(&config, 0, sizeof(config));
+
 	if (dma->direction == DMA_DEV_TO_MEM) {
 		sdd = container_of((void *)dma,
 			struct s3c64xx_spi_driver_data, rx_dma);