The Discovery STM32469I advertises that it comes with 16mb of ram. However, the discovery firmware only enables 11 bits so it only sees 8mb.
You can change line 168 to this and it will fix it
//sdramHandle.Init.RowBitsNumber = FMC_SDRAM_ROW_BITS_NUM_11;
sdramHandle.Init.RowBitsNumber = FMC_SDRAM_ROW_BITS_NUM_12;
Its been a few years so not sure why no one has caught this one considering its one of the few, if not only, discovery devices that have more than 8mb of SDRAM.
You might also want to change SDRAM_DEVICE_SIZE in the header but I don't see it used in many places