radix tree test suite: Fix leaks in regression2.c

None of the malloc'ed data structures were ever being freed.  Found with
-fsanitize=address.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Rehas Sachdeva <aquannie@gmail.com>

tools/testing/radix-tree/regression2.c

@@ -103,7 +103,7 @@ void regression2_test(void)
 
 	/* 4. */
 	for (i = max_slots - 1; i >= 0; i--)
-		radix_tree_delete(&mt_tree, i);
+		free(radix_tree_delete(&mt_tree, i));
 
 	/* 5. */
 	// NOTE: start should not be 0 because radix_tree_gang_lookup_tag_slot
@@ -114,7 +114,9 @@ void regression2_test(void)
 		PAGECACHE_TAG_TOWRITE);
 
 	/* We remove all the remained nodes */
-	radix_tree_delete(&mt_tree, max_slots);
+	free(radix_tree_delete(&mt_tree, max_slots));
+
+	BUG_ON(!radix_tree_empty(&mt_tree));
 
 	printv(1, "regression test 2, done\n");
 }