drm/amdgpu: support fill mem for LSDMA
Support constant data filling in PIO mode for LSDMA.
Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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