The way to configure the DMA mode on DA8xx is different from DSPS.
Add a new function to configure DMA mode on DA8xx and use a callback
to call the right function based on the platform.

Cc: stable@vger.kernel.org  # v4.12+
Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
Tested-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>