drm/amdgpu: send SDMA/GFX IB tests directly to the ring again

There is no point in sending them through the scheduler.

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