drm/amdgpu: cleanup skipping IB test on KIQ

Instead of hard coding the ring type in the function just never provide
a test_ib callback.

Additional to that remove the emit_ib callback to make sure the nobody
ever tries to execute an IB on the KIQ.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>