Provide a positive list of requirements

[xypron]

In the EBBR we require to implement everything that is in chapter "2.6 Requirements" of the UEFI spec if it is not explicitly excluded in the EBBR.

• This requires scope that is far too big for the embedded use case.
• This is not easily testable because of the many cross references in the UEFI spec.
• It is a scope that U-Boot will never implement.

We should return to a positive list of requirements.

Here are examples of what should be discussed:

• support for EFI_LOAD_FILE_PROTOCOL and EFI_LOAD_FILE2_PROTOCOL in LoadImage()
• support for EFI_PLATFORM_DRIVER_OVERRIDE_PROTOCOL and EFI_DRIVER_FAMILY_OVERRIDE_PROTOCOL in ConnectController()
• supported nodes in EFI_DEVICE_PATH_TO_TEXT_PROTOCOL

Especially for protocols to be implemented we need a list identifying the once really needed to be implemented. Protocols required by chapter 2.6 and not implemented in U-Boot include for example:

• EFI_DISK_IO_PROTOCOL
• EFI_NETWORK_INTERFACE_IDENTIFIER_PROTOCOL
• EFI_EDID_DISCOVERED_PROTOCOL
• EFI_EDID_ACTIVE_PROTOCOL

[glikely]

The RNG protocol requirement should also be reflected here.