The point is, there is currently a broken firmware in the flash. So, I have to rely on the recovery boot mode, which I assume is starting even without any firmware at all. In the IMX6 manual it is stated, I have to pull some pin to high-level. Also the pin-number is stated there. However, IMX6 SOC is directly soldered to the PCB, leaving no way to access its pins. If there is now way to set that pin, the device seem to be really bricked, without any way to bring it back to live again.