xfs: use the state defines in xfs_bmap_del_extent_real

Use the same defines as the other extent add and delete helpers, which
both improves code readability and trace point output.

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>