Implement a DMA slave config prepare routine, as until now the MSP
driver depended on the DMA controller completing the channel
configuration on its own, but this is not the case anymore since the
recent DMA driver updates.
Signed-off-by: NFabio Baltieri <fabio.baltieri@linaro.org>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NMark Brown <broonie@linaro.org>