f2fs: compress: fix to check unreleased compressed cluster

Compressed cluster may not be released due to we can fail in
release_compress_blocks(), fix to handle reserved compressed
cluster correctly in reserve_compress_blocks().

Fixes: 4c8ff709

 ("f2fs: support data compression")
Signed-off-by: Sheng Yong <shengyong@oppo.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>