drm/amdgpu/discovery: set the APU flag for GC 11.0.4

Set the APU flag appropriately for GC 11.0.4.

Signed-off-by: Yifan Zhang <yifan1.zhang@amd.com>
Reviewed-by: Aaron Liu <aaron.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>