via-velocity: remove the bounce buffers

Executive summary: the bounce buffers are in my way

- they use something like a 64 * 1500 bytes area of PCI
  consistent area
- they are not resized when the MTU changes
- they are used
  - to hand-pad undersized packets. skb_pad anyone ?
  - to linearize fragmented skbs whose fragment count
    goes beyond the 7 fragments hardware limit in order
    to claim scatter-gather support

Actually the SG code is commented out and I wonder if it
could not be implemented (ab-)using the large send feature
of the chipset since the latter should support some
multi-descriptor packet transmitting.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Fixed-by: Séguier Régis <rseguier@e-teleport.net>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>