[FS#1276] ipq806x: TP-Link C2600 device bricked after sysupgrade

[LEDE Bugs]

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

User who did this - NotTheEvilOne (NotTheEvilOne) 

Attached to Project - OpenWrt/LEDE Project
Summary - ipq806x: TP-Link C2600 device bricked after sysupgrade
Task Type - Bug Report
Category - Kernel
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Critical
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - TP-Link C2600 (and most likely others of ipq806x) broke with one of the last commits. The device in question does not boot anymore. All LEDs stays active so pre-kernel checks fail or it panics (red internet LED does not light up before being reset by kernel).

As no serial connection is available I currently just guess it is due to the following merge:
- commit 33f09cf15178cf7e05cbe816e1cb492bcae89836
  ipq806x: convert to dt-based board-detection 

Is the use of SUPPORTED_DEVICES += instead of SUPPORTED_DEVICES := intended?

The factory image is malformed as well. No checksums were present before the change as far as I can see from LEDE 17.01.4 or sysupgrade image from 05.01.2018. Last known snapshot is from 06.01. or 07.01.2018.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1276