mmc: dw_mmc: change idmac descriptor files to __le32
The dw_mmc driver does not take into account the processor may be in
big endian when writing the descriptors. Change the descriptors for
the 32bit IDMA to use __le32 and ensure they are suitably swapped
before writing.
Note, this has not been tested as the socfpga driver does not try to
use idma.