drm/amdgpu: align GTT start to 4GB v2

For VCE to work properly the start of the GTT space must be aligned to a
4GB boundary.

v2: add comment why we do this

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>
1 file changed