Merge tag 'efi-2019-10-rc1-2' of https://gitlab.denx.de/u-boot/custodians/u-boot-efi

Pull request for UEFI sub-system for v2019.10-rc1 (2)

* Implement the EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE event.
* Address errors of type -Werror=address-of-packed-member when building
  with GCC9.1
* Fix an error when adding memory add addres 0x00000000.
* Rework some code comments for Sphinx compliance.