Merge tag 'uniphier-v2020.04-3' of https://gitlab.denx.de/u-boot/custodians/u-boot-uniphier

UniPhier SoC updates for v2020.04 (3rd)

 - Enable ADMA and HS400 for the eMMC driver on 64-bit SoCs

 - Add some convenient environment variables to handle SD card

 - Sanitize the NAND controller reset sequence and its WP handling

 - Sync DT with Linux