Merge tag 'efi-2021-10-rc2-2' of https://source.denx.de/u-boot/custodians/u-boot-efi

Pull request for efi-2021-10-rc2-2

Documentation:

* Require Sphinx >= 2.4.4 for 'make htmldocs'
* Move devicetree documentation to restructured text and update it
* Document stm32mp1 devicetree bindings

UEFI

* Extend measurement to UEFI variables and ExitBootServices()
* Support Uri() node in devicetree to text protocol
* Add Linux magic token to RISC-V EFI test binaries