drm/amdgpu: Check aca enabled inside cper init/fini func

Move code about checking aca enabled to the cper init/fini function
to make code clean.

Signed-off-by: Xiang Liu <xiang.liu@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>