radix-tree: fix radix_tree_dump() for multi-order entries

- Print which indices are covered by every leaf entry
 - Print sibling entries
 - Print the node pointer instead of the slot entry
 - Build by default in userspace, and make it accessible to the test-suite

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/radix-tree/test.h

@@ -40,5 +40,6 @@ extern int nr_allocated;
 
 /* Normally private parts of lib/radix-tree.c */
 void *indirect_to_ptr(void *ptr);
+void radix_tree_dump(struct radix_tree_root *root);
 int root_tag_get(struct radix_tree_root *root, unsigned int tag);
 unsigned long radix_tree_maxindex(unsigned int height);