xfs_db: metadump should handle symlinks properly

xfs_db: metadump should handle symlinks properly

Remote symlink target blocks are multi-fsb objects on XFS v5 filesystems
because we only write one rmt header per data fork extent.  For fs
blocksize >= 2048 we never have more than one block and therefore nobody
noticed, but for blocksize == 1024 this is definitely not true and leads
to metadump spraying error messages about symlink block crc errors.
Therefore, reformulate the symlink metadump into a multi-fsb dump
function.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
[sandeen: shrink the map declaration]
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>