mmc: sdhi/tmio: switch to using dmaengine_slave_config()

This removes the deprecated use of the .private member of struct dma_chan
and switches the sdhi / tmio mmc driver to using the
dmaengine_slave_config() channel configuration method.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>