Merge tag 'signed-efi-v2018.03' of git://github.com/agraf/u-boot

Patch queue for efi in 2018.03 - 2018-02-10

This time we have a few important bug fixes. Most noticable are:

  - Fix OpenBSD loader with CONFIG_BLK=n
  - Fix builds on various circumstances
  - Add missing stubs so callers don't call NULL
  - Bump UEFI revision to 2.7