drm/amdgpu: Issue ras enable_feature for gfx ip only

For non-GFX IP blocks, set up ras obj if ras feature
is allowed. For GFX IP blocks, force issue ras
enable_feature command to firmware and only set up ras
obj if ras feature is allowed

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>