spi: s3c64xx: move to generic dmaengine API

The spi-s3c64xx uses a Samsung proprietary interface for
talking to the DMA engine, which does not work with
multiplatform kernels.

This version of the patch leaves the old code in place,
behind an #ifdef. This can be removed in the future,
after the s3c64xx platform start supporting the regular
dmaengine interface. An earlier version of this patch was
tested successfully on exynos5250 by Padma Venkat.

The conversion was rather mechanical, since the samsung
interface is just a shallow wrapper around the dmaengine
interface.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/linux/platform_data/spi-s3c64xx.h

@@ -11,6 +11,8 @@
 #ifndef __S3C64XX_PLAT_SPI_H
 #define __S3C64XX_PLAT_SPI_H
 
+#include <linux/dmaengine.h>
+
 struct platform_device;
 
 /**
@@ -38,6 +40,7 @@ struct s3c64xx_spi_info {
 	int src_clk_nr;
 	int num_cs;
 	int (*cfg_gpio)(void);
+	dma_filter_fn filter;
 };
 
 /**