[LIBS] VFS: Upgrade Ext2 filesystem to Ext4 filesystem

This patch does few fixes to Ext2 filesystem to upgrades it to Ext4 filesystem.

The patch also restructures original Ext2 code to make it more manageable and readable.

The current implementation supports Ext4 without journaling and directory indexing but we can mount Ext2 and Ext3 using the Ext4 filesystem.

Signed-off-by: Anup Patel <anup@brainfault.org>