BugLink: https://launchpad.net/bugs/1512997

For Edge Gateway 5000/5100 only.

Add code for controlling WiFi LED via firmware, and turns the LED on
and off when the interface is up and down accordingly.
Signed-off-by: Wen-chien Jesse Sung <jesse.sung@canonical.com>
Reviewed-By: AceLan Kao <acelan.kao@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>