drm/amdgpu: fix amdgpu_bo_gpu_accessible()

The test was relaxed a bit to much.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-and-Tested-by: Roger He <Hongbo.He@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>