igb: set vf rlpml wasn't taking vlan tag into account

This patch updates things so that vlan tags are taken into account when
setting the receive large packet maximum length.  This allows the VF driver
to correctly receive full sized frames when vlans are enabled.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>