Merge tag 'u-boot-stm32-mcu-20190514' of https://github.com/pchotard/u-boot

STM32 MCUs update:
_ Add MPU region for SPI NOR memory mapped region
_ Add missing QSPI flash compatible for STM32 F7 boards
_ Update spi-tx-bus-width and spi-rx-bus-width properties
_ Add QSPI support for STM32F469 Discovery board