mmc: sh_mmcif: switch to the new DMA channel allocation and configuration

Using the "private" field from struct dma_chan is deprecated. The sh
dmaengine driver now also supports the preferred DMA channel allocation
and configuration method, using a standard filter function and a channel
configuration operation. This patch updates sh_mmcif to use this new
method.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Chris Ball <cjb@laptop.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>