xfs: set the prev pointer when reinserting an inode on the unlinked list

xfs: set the prev pointer when reinserting an inode on the unlinked list

If we find a rogue free inode and decide to reinsert it into the
unlinked list, we need to set the prev pointer to NULLAGINO so that the
incore list gets updated.

Cc: stable@vger.kernel.org # v6.10
Fixes: ab97f4b1c03075 ("xfs: repair AGI unlinked inode bucket lists")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>