drm/amdgpu: move preamble IB handling into common code

This fixes the handling which was completely broken when you
ad more than one preamble IB.

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