btrfs: manage check_int_print_mask mount option as %u

As check_int_print_mask mount option is unsigned so manage it as %u for
token verifications, instead of %d.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>