GPI DMA is one of the DMA modes supported on geni, this adds support to
enable that mode
Also do better documentation of the enum geni_se_xfer_mode.
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210625052213.32260-3-vkoul@kernel.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>