btrfs: unlock all the pages with successful inline extent creation

btrfs: unlock all the pages with successful inline extent creation

Since 4750af3bbe5d ("btrfs: prevent extent_clear_unlock_delalloc() to
unlock page not locked by __process_pages_contig()") we have been
unlocking the locked page manually instead of via
extent_clear_unlock_delalloc() because of subpage blocksize support.
However we actually disable inline extent creation for subpage blocksize
support, so this behavior isn't necessary.  Remove this code and
comment, if at some point the subpage blocksize code grows support for
inline extents this can be re-evaluated.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>