drm/amdgpu: move GART struct and function into amdgpu_gart.h v2

No functional change, just cleanup.

v2: rebased, keep gart name.

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