enic: Bug Fix: Change hardware ingress vlan rewrite mode

The current ingress vlan rewrite mode setting lets the hardware strip off
the tag control information of a packet received on native vlan. As a
result, the priority bits are also lost. The fix is to change the ingress
vlan rewrite mode setting such that the complete tag control information is
retained for packets that belong to native vlan.

Signed-off-by: Scott Feldman <scofeldm@cisco.com>
Signed-off-by: Vasanthy Kolluri <vkolluri@cisco.com>
Signed-off-by: Roopa Prabhu <roprabhu@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>