[media] s5p-mfc: Replace bank1/bank2 entries with an array

Internal MFC driver device structure contains two entries for keeping
addresses of the DMA memory banks. Replace them with the dma_base[] array
and use defines for accessing particular banks. This will help to simplify
code in the next patches.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Andrzej Hajda <a.hajda@samsung.com>
Tested-by: Smitha T Murthy <smitha.t@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>