UPSTREAM: firmware: arm_ffa: Add initial Arm FFA driver support

This just add a basic driver that sets up the transport(e.g. SMCCC),
checks the FFA version implemented, get the partition ID for self and
sets up the Tx/Rx buffers for communication.

Link: https://lore.kernel.org/r/20210521151033.181846-3-sudeep.holla@arm.com


Tested-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
(cherry picked from commit 3bbfe987)
Change-Id: Ia42f16e6ba8d6cea06421ba4db9f9778b8fdc266
Bug: 168585974
Signed-off-by: Will Deacon <willdeacon@google.com>