drm/amdgpu: remove some repeated includings

Remove two repeated includings in line 46 and 47.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>