drm/ttm: fix eviction valuable range check.

commit fea456d upstream.

This was adding size to start, but pfn and start are in pages,
so it should be using num_pages.

Not sure this fixes anything in the real world, just noticed it
during refactoring.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20201019222257.1684769-2-airlied@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -761,7 +761,7 @@ bool ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
 	/* Don't evict this BO if it's outside of the
 	 * requested placement range
 	 */
-	if (place->fpfn >= (bo->mem.start + bo->mem.size) ||
+	if (place->fpfn >= (bo->mem.start + bo->mem.num_pages) ||
 	    (place->lpfn && place->lpfn <= bo->mem.start))
 		return false;