Fixes for 5.18-rc1:
 - Fix some incorrect mapping state being passed to iomap during COW
 - Don't create bogus selinux audit messages when deciding to degrade
   gracefully due to lack of privilege
 - Fix setattr implementation to use VFS helpers so that we drop setgid
   consistently with the other filesystems
 - Fix link/unlink/rename to check quota limits
 - Constify xfs_name_dotdot to prevent abuse of in-kernel symbols