gallium/radeon: disallow exports of sparse and suballocated BOs

I think it's unsafe, because the slabs can reuse exported storage.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

src/gallium/winsys/amdgpu/drm/amdgpu_bo.c

@@ -1365,10 +1365,9 @@ static bool amdgpu_bo_get_handle(struct pb_buffer *buffer,
    enum amdgpu_bo_handle_type type;
    int r;
 
-   if (!bo->bo) {
-      offset += bo->va - bo->u.slab.real->va;
-      bo = bo->u.slab.real;
-   }
+   /* Don't allow exports of slab entries and sparse buffers. */
+   if (!bo->bo)
+      return false;
 
    bo->u.real.use_reusable_pool = false;
 

src/gallium/winsys/radeon/drm/radeon_drm_bo.c

@@ -1290,10 +1290,9 @@ static bool radeon_winsys_bo_get_handle(struct pb_buffer *buffer,
     struct radeon_bo *bo = radeon_bo(buffer);
     struct radeon_drm_winsys *ws = bo->rws;
 
-    if (!bo->handle) {
-        offset += bo->va - bo->u.slab.real->va;
-        bo = bo->u.slab.real;
-    }
+    /* Don't allow exports of slab entries. */
+    if (!bo->handle)
+        return false;
 
     memset(&flink, 0, sizeof(flink));