xfs: refactor inode update in iunlink_remove

In xfs_iunlink_remove we have two identical calls to
xfs_iunlink_update_inode, so move it out of the if statement to simplify
the code some more.

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