ARM: mach-shmobile: add DMA for MMCIF on mackerel

Add DMA mode support for the MMCIF controller on mackerel.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>