# Reference http://www.linuxlinx.com/2016/08/fix-no-wireless-on-macbook-after.html
# Removing bcmwl-kernel-source package, then reboot.
sudo apt-get remove --purge bcmwl-kernel-source
sudo reboot
# Installing new broadcom firmware.
sudo apt-get install firmware-b43-installer
# Reaload package.
sudo modprobe -r b43
sudo modprobe b43
# Reboot once again and next after booting you should have BroadCom 4331 Wireless drivers installed and ready to use.
sudo reboot