Merge tag 'u-boot-stm32-20201209' of https://gitlab.denx.de/u-boot/custodians/u-boot-stm

- Manage CONFIG_ENV_EXT4_DEVICE_AND_PART in stm32mp1 board
- Update ARM STI and ARM STM STM32MP Arch maintainers emails
- Enable internal pull-ups for SDMMC1 on DHCOM SoM