kernel code test: reboot notifier test
kernel code test: remove proc file in rmmod

In last commit, it creates a new proc file and change the name, while it
forget to do some change in module unregister.

This patch fix it.
kernel code reading: three fundamental functions for notification chain
kernel code reading: register final callback in net_dev_init()
userspace code example: how to get the ip of local interfaces
kernel code reading: cleanup the net_rx_tx_action

Make this file more clean. Focus on the big view of rx/tx.
kernel code reading: net_sch

This file is more focused on Qdisc and how packets are sent out.