phytec-eeprom-flashtool

PEEPFT-13 phytec_eeprom_flashtool.py: return bytes literals for default MAC address

In the transition from Python 2 to Python 3, the method for
counting bits in the MAC address was changed. This method
requires the default/fallback MAC address to be returned as
a bytes literal or the script will fail.

Signed-off-by: Matt McKee <mmckee@phytec.com>