I'm having the same stack trace with a 2 Amp 5v adapter connected to the expansion dock (also tried a usb wire directly to my pc), but I don't seem to have any problems with accessing the web ui or turning itself off. I have yet to connect any usb peripherals.
[ 11.254083] ------------[ cut here ]------------
[ 11.258782] WARNING: CPU: 0 PID: 476 at drivers/spi/spidev.c:719
init_module+0x533c/0x5dec [spidev]()
...
[ 11.649524] ---[ end trace 2720e5d9d588bb52 ]---