drm/amdgpu: add license to files where it was missing

These files were missing it before.

Acked-by: Harry Wentland <[email protected]>
Acked-by: Felix Kuehling <[email protected]>
Acked-by: Christian König <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
15 files changed