xfs: remove redundant set null for ip->i_itemp

ip->i_itemp has been set null in xfs_inode_item_destroy(), so there is
no need set it null again in xfs_inode_free_callback().

Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: Long Li

fs/xfs/xfs_icache.c

@@ -159,7 +159,6 @@ xfs_inode_free_callback(
 		ASSERT(!test_bit(XFS_LI_IN_AIL,
 				 &ip->i_itemp->ili_item.li_flags));
 		xfs_inode_item_destroy(ip);
-		ip->i_itemp = NULL;
 	}
 
 	kmem_cache_free(xfs_inode_cache, ip);