arm_ffa: efi: corstone1000: enable MM communication

turn on EFI MM communication

On Corstone-1000 platform MM communication between u-boot
and the secure world (Optee) is done using the FF-A bus.

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