mmc: mediatek: add 64G DRAM DMA support

MT2712 MSDC supports 64G DRAM DMA access, it needs update
gpd/bd structure.

Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>