For IQD we already need to fix up the qeth_hdr's length field, and
future changes will require more flexibility for OSA as well. The
device-specific path knows best what header length it requires, so just
pass it from there.
While at it, remove the unused qeth_card parameter.

No functional change.
Signed-off-by: NJulian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>