f2fs: fix spelling mistake: "extenstion" -> "extension"

Trivial fix to spelling mistake in extension list text

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
1 file changed