sdmmc driver: fix clock rate calculation
sdmmc driver: fix clock rate calculation

hoangt/NyuziProcessor,jbush001/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor,hoangt/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor,hoangt/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,hoangt/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor