xfs: fix up inode cowblocks tracking tracepoints

These calls are still using the eofblocks tracepoints. The cowblocks
equivalents are already defined, we just aren't actually calling them.

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