xfs: increase rename inode reservation

xfs_rename can update up to 5 inodes: src_dp, target_dp, src_ip, target_ip
and wip.  So we need to increase the inode reservation to match.

Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>