xfs: pass a struct xfs_bmbt_irec to xfs_bmbt_lookup_eq

Now that we've massaged the callers into the right form we can always
pass the actual extent record instead of the individual fields.

As an additional benefit the btree cursor will now be prepoulated with
the correct extent state instead of having to fix it up later.

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