f2fs: compress: fix to assign compress_level for lz4 correctly

After remount, F2FS_OPTION().compress_level was assgin to
LZ4HC_DEFAULT_CLEVEL incorrectly, result in lz4hc:9 was enabled, fix it.

1. mount /dev/vdb
/dev/vdb on /mnt/f2fs type f2fs (...,compress_algorithm=lz4,compress_log_size=2,...)
2. mount -t f2fs -o remount,compress_log_size=3 /mnt/f2fs/
3. mount|grep f2fs
/dev/vdb on /mnt/f2fs type f2fs (...,compress_algorithm=lz4:9,compress_log_size=3,...)

Fixes: 00e120b ("f2fs: assign default compression level")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: chaseyu

fs/f2fs/super.c

@@ -591,7 +591,7 @@ static int f2fs_set_lz4hc_level(struct f2fs_sb_info *sbi, const char *str)
 	unsigned int level;
 
 	if (strlen(str) == 3) {
-		F2FS_OPTION(sbi).compress_level = LZ4HC_DEFAULT_CLEVEL;
+		F2FS_OPTION(sbi).compress_level = 0;
 		return 0;
 	}