XArray updates for 5.4

These patches all fix various bugs, some of which people have tripped
over and some of which have been caught by automatic tools.

Matthew Wilcox (Oracle) (5):
  XArray: Fix xas_next() with a single entry at 0
  idr: Fix idr_get_next_ul race with idr_remove
  radix tree: Remove radix_tree_iter_find
  idr: Fix integer overflow in idr_for_each_entry
  idr: Fix idr_alloc_u32 on 32-bit systems