ACPICA: Add start method for ARM FF-A

Add TPM start method for ARM FF-A defined in the TCG ACPI specification
v1.4.

See: https://trustedcomputinggroup.org/wp-content/uploads/TCG-ACPI-Specification-Version-1.4-Revision-15_pub.pdf

[jarkko:
 1. Fine-tuned the commit message.
 2. Added link to the TCG ACPI specification.]

Link: https://github.com/acpica/acpica/pull/1000


Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>