Treat it like ATIF and check both the dGPU and APU for
the method.  This is required because ATCS may be hung
off of the APU in ACPI on A+A systems.

v2: add back accidently removed ACPI handle check.
v3: Fix incorrect atif check (Colin)
    Fix uninitialized variable (Colin)
Reviewed-by: NLijo Lazar <lijo.lazar@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>