btrfs: fix a memory allocation failure test in btrfs_submit_direct

btrfs: fix a memory allocation failure test in btrfs_submit_direct

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

Fixes: 37b562d495cf ("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>