bna: allow transmit tagged frames

When Tx VLAN offloading is disabled frames with size ~ MTU are not
transmitted as the driver does not account 4 bytes of VLAN header added
by stack. It should use VLAN_ETH_HLEN instead of ETH_HLEN.

The second problem is with newer BNA chips (BNA 1860). These chips filter
out any VLAN tagged frames in Tx path. This is a problem when Tx VLAN
offloading is disabled and frames are tagged by stack. Older chips like
1010/1020 are not affected as they probably don't do such filtering.

Cc: Rasesh Mody <rasesh.mody@qlogic.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>