drm/amd/amdgpu: Add APU flag to gca_config debugfs data (v3)

Needed by umr to detect if ip discovered ASIC is an APU or not.

(v2): Remove asic type from packet it's not strictly needed
(v3): Correct comment

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>