Merge tag 'efi-2022-04-rc1-3' of https://source.denx.de/u-boot/custodians/u-boot-efi

Pull request for efi-2022-04-rc1-3

Documentation:

* update Nokia RX-51 documentation and move it to rst
* describe boot switch settings for HiFive Unmatched board

UEFI:

* fix the checking of images hashes and signatures
* provide the RISCV_EFI_BOOT_PROTOCOL