arm_ffa: efi: introduce FF-A MM communication

arm_ffa: efi: introduce FF-A MM communication

Add MM communication support using FF-A transport

This feature allows accessing MM partitions services through
EFI MM communication protocol. MM partitions such as StandAlonneMM
or smm-gateway secure partitions which reside in secure world.

An MM shared buffer and a door bell event are used to exchange
the data.

The data is used by EFI services such as GetVariable()/SetVariable()
and copied from the communication buffer to the MM shared buffer.

The secure partition is notified about availability of data in the
MM shared buffer by an FF-A message (door bell).

On such event, MM SP can read the data and updates the MM shared
buffer with the response data.

The response data is copied back to the communication buffer and
consumed by the EFI subsystem.

MM communication protocol supports FF-A 64-bit direct messaging.

We tested the FF-A MM communication on the Corstone-1000 platform.

We ran the UEFI SCT test suite containing EFI setVariable, getVariable and
getNextVariable tests which involve FF-A MM communication and all tests
are passing with the current changes.

We made the SCT test reports (part of the ACS results) public following the
latest Corstone-1000 platform software release. Please find the test
reports at [1].

[1]: https://gitlab.arm.com/arm-reference-solutions/arm-reference-solutions-test-report/-/tree/master/embedded-a/corstone1000/CORSTONE1000-2023.06/acs_results_fpga.zip

Signed-off-by: Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
Tested-by: Gowtham Suresh Kumar <gowtham.sureshkumar@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>