xfs: use correct state defines in xfs_bmap_del_extent_{cow,delay}

Use the _FILLING values to match the usage in the xfs_bmap_add_extent_*
helpers.  No change in behavior, just better naming in the code and
tracepoint output.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Brian Foster <bfoster@redhat.com>
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>