This patch makes it possible to configure and limit per-client internet
speed based on MAC address and it can work with SQM.
This feature is what OpenWRT currently lacks. This patch is largely based
on static.sh and the configuration file is similar to original nft-qos.

New configuration options and examples are listed below

config default 'default'
    option limit_mac_enable '1'
config client
	option drunit 'kbytes'
	option urunit 'kbytes'
	option hostname 'tv-box'
	option macaddr 'AB:CD:EF:01:23:45'
	option drate '1000'
	option urate '50'
config client
	option drunit 'kbytes'
	option urunit 'kbytes'
	option hostname 'my-pc'
	option macaddr 'AB:CD:EF:01:23:46'
	option drate '3000'
	option urate '2000'

limit_mac_enable - enable rate limit based on MAC address
drunit - download rate unit
urunit - upload rate unit
macaddr - client MAC address
drate - download rate
urate - upload rate

Signed-off-by: Tong Zhang <ztong0001@gmail.com>

This is the nftables implementation for qos on OpenWrt,
Currently, it has below features:

* Static QoS : setting limit rate for devices or global network.

* Dynamic/Auto QoS : setting limit rate according to the network
  bandwidth and adjust itself automatically (hotplug event).

* Traffic Priority : this feature is like traffic shaping under tc,
  it uses ingress hook to handle to packets here.

Signed-off-by: Rosy Song <rosysong@rosinson.com>