* generate_boot_image.sh requires root rights at many different points
* in it possible that the sudo timeout hits in between, leading to
  aborted execution if the user fails to re-enter the password
* fixed that, asking once, re-using the password
* also fixed and improved several other things:
* fixed zedboard and zc706 devicetrees (needed patching to activate IRQs)
* same with PyNQ, but different approach: have fixed devicetree in pynq
* fixed U-Boot output log redirection