xfs: updates for 4.10-rc1

Contained in this update:
- DAX PMD vaults via iomap infrastructure
- Direct-io support in iomap infrastructure
- removal of now-redundant XFS inode iolock, replaced with VFS i_rwsem
- synchronisation with fixes and changes in userspace libxfs code
- extent tree lookup helpers
- lots of little corruption detection improvements to verifiers
- optimised CRC calculations
- faster buffer cache lookups
- deprecation of barrier/nobarrier mount options - we always use
  REQ_FUA/REQ_FLUSH where appropriate for data integrity now
- cleanups to speculative preallocation
- miscellaneous minor bug fixes and cleanups
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Merge branch 'xfs-4.10-misc-fixes-4' into for-next