add support to handle ATCS method for power shift control.
used to communicate dGPU device state to SBIOS.

V2: use defined acpi func for checking psc support (Lijo)
    fix alignment (Shashank)
V3: rebased on unified ATCS handling (Alex)
V4: rebased on ATPX/ATCS structures global (Alex)
Signed-off-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>