avrdude: ser_open(): can't open device "usb": The system cannot find the file specified
Figured out the problem. The command needs to be:
avrdude -p m328p -c avrispmkII -P usb -B 15.625 -U flash:w:firmware.hex:a -U lfuse:w:0xd6:m -U hfuse:w:0xd8:m -U efuse:w:0x07:m
It now uses the usb port.