qlge: Enhance nested VLAN (Q-in-Q) handling.

o Adapter doesn’t handle packets with nested VLAN tags in
Rx path. User can turn off VLAN tag stripping in the hardware
and let the stack handle stripping of VLAN tags in the Rx path.

o Users can enable or disable hardware VLAN acceleration using ethtool

Signed-off-by: Jitendra Kalsaria <jitendra.kalsaria@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>