Getting the same error as OP, with very similar setup so far except using BBB and using Debian GNU/Linux 8 2016-01-24
When I try to flash the firmware using (make flash_firmware) I get an error though. I’m relatively new with BBB, so I’m not sure if there are other ways to ‘flash the firmware.’
Thanks in advance.
EDIT: I have tried using chmod a+x to give me permission to execute, and then came across a problem with dev/tty02 in the flasher, which I changed to dev/tty2 (to match what was in my /dev list), but still no luck in successfully flashing the firmware.