qeth: avoid skb_under_panic for malformatted inbound data

To make the qeth driver more robust in case of malformatted inbound
packets due to hardware problems, an additional check for
OSN-card-type is added for OSN-type packets.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>