BUGfix: wrong configuration selection by incomplete macro

As datasheet for ATmega128 (http://www.atmel.com/Images/doc2467.pdf)
indicates, INT0 is located at PD0 instead of PD2.
So "USB_CFG_INTPORT_BIT" is the same as for ATmega640,
ATmega1280, ATmega1281, ATmega2560 and ATmega2561.

Special thanks to trkien, who indirectly indicated this BUG to me in:
http://forums.obdev.at/viewtopic.php?f=8&t=8691&sid=020c08aa877e11fdd65d9b1638ac5bd3#p26140

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>