xfs: add an entries pointer to struct xfs_dir3_icleaf_hdr

All callers of the ->node_tree_p dir operation already have a struct
xfs_dir3_icleaf_hdr from a previous call to xfs_da_leaf_hdr_from_disk at
hand, or just need slight changes to the calling conventions to do so.
Add a pointer to the entries to struct xfs_dir3_icleaf_hdr to clean up
this pattern.  To make this possible the xfs_dir3_leaf_log_ents function
grow a new argument to pass the xfs_dir3_icleaf_hdr that call callers
already have, and xfs_dir2_leaf_lookup_int returns the
xfs_dir3_icleaf_hdr to the callers so that they can later use it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>