f2fs: change compr_blocks of superblock info to 64bit

Current compr_blocks of superblock info is not 64bit value. We are
accumulating each i_compr_blocks count of inodes to this value and
those are 64bit values. So, need to change this to 64bit value.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>