btrfs: fix a memory allocation failure test in btrfs_submit_direct

After allocation 'dip' is tested instead of 'dip->csums'.  Fix it.

Fixes: 642c5d34 ("btrfs: allocate the btrfs_dio_private as part of the iomap dio bio")
CC: stable@vger.kernel.org # 5.19+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -7980,7 +7980,7 @@ static void btrfs_submit_direct(const struct iomap_iter *iter,
 		 */
 		status = BLK_STS_RESOURCE;
 		dip->csums = kcalloc(nr_sectors, fs_info->csum_size, GFP_NOFS);
-		if (!dip)
+		if (!dip->csums)
 			goto out_err;
 
 		status = btrfs_lookup_bio_sums(inode, dio_bio, dip->csums);