include/mmc.h: remove struct mmc_csd

The outdated struct mmc_csd was only used by old atmel_mci driver which was
removed in c9abb4260c30fbfd51bb2cd551e7426e2ae15b66.

Signed-off-by: Andreas Bießmann <biessmann@corscience.de>
cc: Andy Fleming <afleming@freescale.com>
1 file changed