The eSDHC can only DMA from 32-bit-aligned addresses.

This fixes the following test cases of mmc_test:
  11:	Badly aligned write
  12:	Badly aligned read
  13:	Badly aligned multi-block write
  14:	Badly aligned multi-block read
Signed-off-by: Benoît Thébaudeau <benoit@wsystem.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>