igb: specify phc_index of 82575 for get_ts_info

82575 has only software timestamping capability and it has
no PTP Hardware Clocks. Therefore, -1 has to be specified
to the phc_index for ethtool's get_ts_info, otherwise a wrong
value will be set to the phc_index.

v2: move the if (adapter->ptp_clock) section specifying phc_index
    to above the switch statement as suggested by Matthew Vick.
    adapter->ptpclock will always be NULL for 82575.
Signed-off-by: Ken ICHIKAWA <ichikawa.ken@jp.fujitsu.com>
Acked-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

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

@@ -2353,6 +2353,11 @@ static int igb_get_ts_info(struct net_device *dev,
 {
 	struct igb_adapter *adapter = netdev_priv(dev);
 
+	if (adapter->ptp_clock)
+		info->phc_index = ptp_clock_index(adapter->ptp_clock);
+	else
+		info->phc_index = -1;
+
 	switch (adapter->hw.mac.type) {
 	case e1000_82575:
 		info->so_timestamping =
@@ -2374,11 +2379,6 @@ static int igb_get_ts_info(struct net_device *dev,
 			SOF_TIMESTAMPING_RX_HARDWARE |
 			SOF_TIMESTAMPING_RAW_HARDWARE;
 
-		if (adapter->ptp_clock)
-			info->phc_index = ptp_clock_index(adapter->ptp_clock);
-		else
-			info->phc_index = -1;
-
 		info->tx_types =
 			(1 << HWTSTAMP_TX_OFF) |
 			(1 << HWTSTAMP_TX_ON);