[FS#692] WLAN AP not working on RasPi (bcm2710 target)

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Thomas Ganter (thomas) 

Attached to Project - LEDE Project
Summary - WLAN AP not working on RasPi (bcm2710 target)
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - All
Due in Version - Undecided
Due Date - Undecided
Details - When flashing the brcm2708 / bcm2710 target the WiFi interface gets stuck in "client mode" and the AP will not be able to be brought up. 

Some screenshots and a load of discussion here: 
https://forum.lede-project.org/t/ap-mode-radio0-in-raspi-3-always-acts-as-a-client-shows-as-wlan0-in-luci/2885

Two more days of tinkering, wifi-up'ing and -down'ing did not bring me further. 
I flashed another Pi3 (to exclude a hardware defect) with the same result. 

I tried latest snapshot and stable images. 
I am happy to help debug  --  tell me what you need me to do. 

Greetings, 
--Thomas

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=692