drm/amdgpu: skip the new gc doorbell function for some asics

This patch will skip the new gc doorbell function for some asics,
only enable new doorbell model on aisc where it is supported.

Signed-off-by: Xiaojian Du <Xiaojian.Du@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>