PoE per port ON/OFF setting

Please follow the method to set PoE on/off

Check the Board ID first, and use i2cset to set the PoE status

## Board ID unchanged, default I2C address 0x21
## PoE turn off
## port 1~4 off
sudo i2cset -y 0 0x21 0x12 0x00
## port 1 off
sudo i2cset -y 0 0x21 0x12 0xfc
## port 2 off
sudo i2cset -y 0 0x21 0x12 0xf3
## port 3 off
sudo i2cset -y 0 0x21 0x12 0xcf
## port 4 off
sudo i2cset -y 0 0x21 0x12 0x3f

## PoE turn ON
## port 1~4 on
sudo i2cset -y 0 0x21 0x12 0xff
sudo i2cset -y 0 0x21 0x14 0xff