Merge tag 'u-boot-imx-20200623' of https://gitlab.denx.de/u-boot/custodians/u-boot-imx

Fixes for 2020.07
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Travis: https://travis-ci.org/github/sbabic/u-boot-imx/builds/701059103

- Fixes for atheros and cubox
- Toradex: mostly environment
- i.MX7: DDR fixes
- switch to DM
- sabrelite : fix MMC access