Merge tag 'efi-2020-01-rc3' of https://gitlab.denx.de/u-boot/custodians/u-boot-efi

Pull request for UEFI sub-system for efi-2020-01-rc3

The following changes for the UEFI subsystem are provided:

* allow building UEFI binaries on the sandbox
* enable access to file systems without partition tables
* correctly check the return value of efi_dp_from_file()