Merge tag 'u-boot-stm32-20190523' of https://github.com/pchotard/u-boot
- Add various STM32MP1 fixes for serial, env, clk, board, i2c ...
- Add STM32MP1 DDR driver update:
These update introduce the DDR interactive mode described in:
https://wiki.st.com/stm32mpu/index.php/U-Boot_SPL:_DDR_interactive_mode
This mode is used by the CubeMX: DDR tuning tool.
https://wiki.st.com/stm32mpu/index.php/STM32CubeMX
The DDR interactive mode is NOT activated by default because
it increase the SPL size and slow down the boot time
(200ms wait added).
