xfs_scrub: use parent pointers to report lost file data

xfs_scrub: use parent pointers to report lost file data

If parent pointers are enabled, compute the path to the file while we're
doing the fsmap scan and report that, instead of walking the entire
directory tree to print the paths of the (hopefully few) files that lost
data.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>