Merge tag 'u-boot-stm32-mcu-20190423' of https://github.com/pchotard/u-boot

STM32 MCUs update:
- DT rework and alignment with DT kernel v4.20
- mmc: arm_pl180_mmci: Synchronize compatible with kernel v4.20
- mmc: stm32_sdmmc2: Synchronize properties with kernel v4.20
- configs: update for F746/769 boards