drm/amdgpu/acpi: make ATPX/ATCS structures global (v2)

They are global ACPI methods, so maybe the structures
global in the driver. This simplified a number of things
in the handling of these methods.

v2: reset the handle if verify interface fails (Lijo)
v3: fix compilation when ACPI is not defined.

Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>