Buffers are allocated in the main ram, which is suitable for use with the
underlying STM32H7 SDMMC1 core in IDMA mode.
Files are copied from stm32f7/nucleo-144.
boards/arm/stm32h7/stm32h747i-disco: Remove references to nucleo in the stm32h747i-disco board.
arch/arm/include/stm32h7, arch/arm/src/stm32h7, and boards/arm/stm32h7/stm32h747i-disco: Add support for the STM32H747I-DISCO board.