Merge tag 'u-boot-stm32-20210312' of https://source.denx.de/u-boot/custodians/u-boot-stm

- Add WATCHDOG_RESET() in MTD framework and STM32 QSPI driver
- stm32mp1_trusted_defconfig rely on SCMI support
- Remove the nand MTD configuration for NOR boot in stm32mp1 board
- STM32programmer update
- Bsec: manage clock when present in device tree
- stm32mp15: move bootdelay configuration in defconfig
- Update for stm32 dsi and dw_mipi_dsi
- STM32 MCU's cleanup
- Fix compilation issue depending on SYS_DCACHE_OFF and SYS_ICACHE_OFF flags
- Update stm32mp1 doc