drivers: gpu: Remove duplicate include of amdgpu_hdp.h

amdgpu_hdp.h has been included at line 91, so remove
the duplicate include.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>