[SqNOS] Net-gera.11: fixed checksum calculations

[Gerardo Richarte]

Name: Net-gera.11
Author: gera
Time: 29 July 2006, 2:03:01 pm
UUID: 5daf5ca7-4093-4aec-b87c-080f16be164a
Ancestors: Net-len.10

fixed checksum calculations:

when the size was odd, the last byte was wrongly added to the sum (in
computeChecksumFrom:to:).
the IPPacket size was used instead of IPPacket length. This two are the
same except when the card returns the padding bytes after the ethernet
packet as part of the packet. This happens on Lance card for packets
with legnth < 60. IPPacket length is the header field, so it's always
correct.