Fix:
drivers/mmc/libmmc.o: In function `mxsmmc_send_cmd':
/home/ag/git/u-boot/drivers/mmc/mxsmmc.c:210: undefined reference to `mxs_dma_desc_append'
/home/ag/git/u-boot/drivers/mmc/mxsmmc.c:211: undefined reference to `mxs_dma_go'
drivers/mmc/libmmc.o: In function `mxsmmc_initialize':
/home/ag/git/u-boot/drivers/mmc/mxsmmc.c:306: undefined reference to `mxs_dma_desc_alloc'