optee: ffa_abi: add asynchronous notifications

Adds support for asynchronous notifications from OP-TEE in secure world
when communicating via FF-A. In principle from OP-TEE and kernel driver
point of view this works in the same way as for the SMC ABI based
implementation.

The OP-TEE FF-A ABI is expanded in OPTEE_FFA_EXCHANGE_CAPABILITIES with
the capability OPTEE_FFA_SEC_CAP_ASYNC_NOTIF to indicate that OP-TEE
supports asynchronous notifications. OPTEE_FFA_ENABLE_ASYNC_NOTIF is
also added to tell that the driver has successfully initialized these
notifications.

Notification capability is negotiated while the driver is initialized.
If both sides supports these notifications then they are enabled.

The notification concept in this driver is merged with the FF-A concept,
the lower 64 values are reserved for FF-A as asynchronous notifications
while the synchronous notifications use the higher values.

So a FF-A notification has to be allocated for each discrete
asynchronous notification value needed. Only one asynchronous
notification value is used at the moment, the "do bottom half"
notification.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>

optee: add FF-A capability OPTEE_FFA_SEC_CAP_ARG_OFFSET

Adds the secure capability OPTEE_FFA_SEC_CAP_ARG_OFFSET to indicate that
OP-TEE with FF-A can support an argument struct at a non-zero offset into
a passed shared memory object.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

optee: add FF-A support

Adds support for using FF-A [1] as transport to the OP-TEE driver.

Introduces struct optee_msg_param_fmem which carries all information
needed when OP-TEE is calling FFA_MEM_RETRIEVE_REQ to get the shared
memory reference mapped by the hypervisor in S-EL2. Register usage is
also updated to include the information needed.

The FF-A part of this driver is enabled if CONFIG_ARM_FFA_TRANSPORT is
enabled.

[1] https://developer.arm.com/documentation/den0077/latest
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>