f2fs: Revert "f2fs: truncate blocks in batch in __complete_revoke_list()"

We should not truncate replaced blocks, and were supposed to truncate the first
part as well.

This reverts commit 78a99fe6.

Cc: stable@vger.kernel.org
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>