via-rhine: hardware VLAN support

This patch adds VLAN hardware support for Rhine chips.

The driver uses up to 3 additional bytes of buffer space when extracting
802.1Q headers; PKT_BUF_SZ should still be sufficient.

The initial code was provided by David Lv. I reworked it to use standard
kernel facilities. Coding style clean up mostly follows via-velocity.

Adapted to new interface for VLAN acceleration (per request of Jesse Gross).
Signed-off-by: David Lv <DavidLv@viatech.com.cn>
Signed-off-by: Roger Luethi <rl@hellgate.ch>

 drivers/net/via-rhine.c |  326 +++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 312 insertions(+), 14 deletions(-)
Signed-off-by: David S. Miller <davem@davemloft.net>