drm/amdgpu: fix amdgpu_bo_pin_restricted VRAM placing v2

We could pin BOs into invisible VRAM otherwise.

v2: make logic more readable as suggested by Michel

Cc: stable@vger.kernel.org
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com> (v1)
Reviewed-by: Rex Zhu <Rex.Zhu@amd.com> (v1)
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_object.c

@@ -399,7 +399,8 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo *bo, u32 domain,
 		}
 		if (fpfn > bo->placements[i].fpfn)
 			bo->placements[i].fpfn = fpfn;
-		if (lpfn && lpfn < bo->placements[i].lpfn)
+		if (!bo->placements[i].lpfn ||
+		    (lpfn && lpfn < bo->placements[i].lpfn))
 			bo->placements[i].lpfn = lpfn;
 		bo->placements[i].flags |= TTM_PL_FLAG_NO_EVICT;
 	}