Merge tag 'efi-2020-04-rc1-2' of https://gitlab.denx.de/u-boot/custodians/u-boot-efi

Pull request for UEFI sub-system for efi-2020-04-rc1-2

Bug fixes for the UEFI sub-system are provided:

* imply VIDEO_ANSI for correct cursor positioning and colors
* fix issues in the UEFI block device driver
* add missing documentation