igb: fix vlan filtering in promisc mode when not in VT mode

This patch fixes a VT mode check to make sure VLAN filters are disabled when
in promisc mode and VT is not enabled.

The problem with the previous check was that:
E1000_MRQC_ENABLE_VMDQ is defined as 0x00000003

but when not in VT mode:
mrqc |= E1000_MRQC_ENABLE_RSS_4Q (0x00000002)

So the above check will trigger regardless if VT mode is being used or not.
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -3739,9 +3739,8 @@ static void igb_set_rx_mode(struct net_device *netdev)
 	rctl &= ~(E1000_RCTL_UPE | E1000_RCTL_MPE | E1000_RCTL_VFE);
 
 	if (netdev->flags & IFF_PROMISC) {
-		u32 mrqc = rd32(E1000_MRQC);
 		/* retain VLAN HW filtering if in VT mode */
-		if (mrqc & E1000_MRQC_ENABLE_VMDQ)
+		if (adapter->vfs_allocated_count)
 			rctl |= E1000_RCTL_VFE;
 		rctl |= (E1000_RCTL_UPE | E1000_RCTL_MPE);
 		vmolr |= (E1000_VMOLR_ROPE | E1000_VMOLR_MPME);