xfs_db: fix nlink usage in check

xfs_db: fix nlink usage in check

process_inode uses a local convenience variable to abstract the
differences between the ondisk nlink fields in a v1 inode and a v2
inode.  Use this variable for checking and reporting errors.

Fixes: 6526f30e4801 ("xfs_db: stop misusing an onstack inode")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>