Merge tag 'efi-2019-04-rc3' of https://github.com/xypron2/u-boot

Merge tag 'efi-2019-04-rc3' of https://github.com/xypron2/u-boot

Pull request for the UEFI sub-system for v2019.04-rc3

A new option -e is added to the env command which allows to display and
change UEFI variables in a user friendly way.

A new command efidebug is introduced to edit the UEFI boot sequence and to
display different aspects of the state of the UEFI sub-system: memory map,
loaded images, handles, drivers and devices.

A bug in the UEFI boot manager is fixed.