Initial DMA support for STM32H7
arch/arm/src/stm32h7: SPI DMA mode
arch/arm/src/stm32h7/chip/stm32h7x3xx_memorymap.h: add base addresses for D1, D2 and D3 domain; use 2 bytes to specify memory region
arch/arm/src/stm32h7/stm32h7x3xx_rcc.c: add D1 domain core prescaler configuration
Approved-by: Gregory Nutt <gnutt@nuttx.org>
sched/init/nx_start.c: Add support for CONFIG_BOARD_DRIVER_INITIALIZE. If this option is selected then nx_start() will call a board-provided function board_driver_initialize() immediately after calling up_initialize().
Rename CONFIG_BOARD_INITIALIZE to CONFIG_BOARD_LATE_INITIALIZE.
Raname board_initialize() to board_late_initialize()
stm32h7
stm32h7: compile with stm32_rcc.c
stm32h7: some PWR definitions
stm32h7: add some RCC defs and change some code style to be more like in other STM ports
stm32h7: basic clocks configuration
Approved-by: GregoryN <gnutt@nuttx.org>