btrfs-progs: remove unused btrfs_raid_profile::max_stripes
    
    The max_stripes value of btrfs_raid_profile_table is unused, so we can
    just remove it as well.
    
    Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
    Signed-off-by: David Sterba <dsterba@suse.com>