mmc: pxamci: remove dma resources from private context

These members are no longer in use, so let's remove them.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>