mmc: sunxi-mmc: change idma descriptor to __le32

The sunxi-mmc driver does not take into account the processor may be big
endian when writing the DMA descriptors. This causes cards not to be
detected when running a big-endian kernel. Change the descriptors for
IDMA to use __le32 and ensure they are suitably swapped before writing.
Tested successfully on the Cubieboard2.

Signed-off-by: Michael Weiser <michael.weiser@gmx.de>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: linux-mmc@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>