mmc: s3cmci: Use DMA slave map rather than exported DMA filter

mmc: s3cmci: Use DMA slave map rather than exported DMA filter

Support for DMA slave map has been added to the s3c24xx-dma
controller in commit 3655c0fdae2027925b054544133a6fada4d0ad5f
"dmaengine: s3c24xx: Add dma_slave_map for s3c2440 devices"
This patch converts the s3cmci driver to also use it, so we can
eventually get rid of the exported filter function once all
related DMA clients are updated.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>