btrfs: zoned: put block group after final usage

It's counter-intuitive (and wrong) to put the block group _before_ the
final usage in submit_eb_page. Fix it by re-ordering the call to
btrfs_put_block_group after its final reference. Also fix a minor typo
in 'implies'

Fixes: be1a1d7a ("btrfs: zoned: finish fully written block group")
CC: stable@vger.kernel.org # 5.16+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>