Allocate headroom for TR_HLEN but using only ETH_HLEN causes rx
performance degradation. Allocate ETH_HLEN for ethernet and
TR_HLEN for token ring (layer 3 mode).
Signed-off-by: NFrank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>