Minimal Cyclone V SE Testsystem on DE0-NANO-SOC: Uboot dies right after FPGA config

Hi, I made a minimum System in Quartus 15.1. The Qsys Systems consist only of an AvalonMM UART and a 8 bit PIO for the LEDs. The only bridge used is the lightweight HPS4FPGA one (in32bit mode)....