igb: fix last_rx_timestamp usage

last_rx_timestamp should be updated only when rx time stamp is
read. Also it's only used with NICs that have per-interface time
stamping resources so it can be moved to adapter structure and
set in igb_ptp_rx_rgtstamp().

Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Acked-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 720ad12..fb98d46 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6954,7 +6954,9 @@
 
 	igb_rx_checksum(rx_ring, rx_desc, skb);
 
-	igb_ptp_rx_hwtstamp(rx_ring, rx_desc, skb);
+	if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TS) &&
+	    !igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP))
+		igb_ptp_rx_rgtstamp(rx_ring->q_vector, skb);
 
 	if ((dev->features & NETIF_F_HW_VLAN_CTAG_RX) &&
 	    igb_test_staterr(rx_desc, E1000_RXD_STAT_VP)) {