radix_tree_iter_resume: Fix out of bounds error

The address sanitizer occasionally finds an out of bounds error while
running the test-suite.  It turned out to be a read of the pointer
immediately next to the tree root, but this out of bounds error could
have occurred elsewhere.  This happens because radix_tree_iter_resume()
dereferences 'slot' before checking whether we've come to the end of
the chunk.  We can just delete this line; the value was never used.
Signed-off-by: NMatthew Wilcox <mawilcox@microsoft.com>

lib/radix-tree.c

@@ -1685,7 +1685,6 @@ void **radix_tree_iter_resume(void **slot, struct radix_tree_iter *iter)
 
 	slot++;
 	iter->index = __radix_tree_iter_add(iter, 1);
-	node = rcu_dereference_raw(*slot);
 	skip_siblings(&node, slot, iter);
 	iter->next_index = iter->index;
 	iter->tags = 0;