drm/amdgpu: Set the correct value for PDEs/PTEs of ATC memory on Raven

Without the additional bits set in PDEs/PTEs, the ATC memory access
would have failed on Raven.

Signed-off-by: Yong Zhao <yong.zhao@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>