linux-phytec-fsl

mmc: atmel-mci: use probe deferring if dma controller is not ready yet

Return probe defer if requesting a dma channel without a dma controller
probed.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>