drm/amdgpu: check GFX RAS capability before reset counters

disallow the logical to be enabled on platforms that
don't support gfx ras at this stage, like sriov skus,
dgpu with legacy ras.etc

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>