[PATCH 22/27] xfs: use generic get_unaligned_beXX helpers

[Christoph Hellwig]

One interestin caveat about inode numers is that the we use the
XFS_DIR2_DATA_FREE_TAG magic number in the firt two bytes of
struct xfs_dir2_data_unused to detect this free space header in all
non-shortform directory formats.  These two bytes overlap with
the inode number in struct xfs_dir2_data_entry.