igc: Fix TX timestamp support for non-MSI-X platforms

Time synchronization was not properly enabled on non-MSI-X platforms.

Fixes: 2c344ae245 ("igc: Add support for TX timestamping")
Signed-off-by: James McLaughlin <james.mclaughlin@qsc.com>
Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Tested-by: Nechama Kraus <nechamax.kraus@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc_main.c

@@ -5467,6 +5467,9 @@ static irqreturn_t igc_intr_msi(int irq, void *data)
 			mod_timer(&adapter->watchdog_timer, jiffies + 1);
 	}
 
+	if (icr & IGC_ICR_TS)
+		igc_tsync_interrupt(adapter);
+
 	napi_schedule(&q_vector->napi);
 
 	return IRQ_HANDLED;
@@ -5510,6 +5513,9 @@ static irqreturn_t igc_intr(int irq, void *data)
 			mod_timer(&adapter->watchdog_timer, jiffies + 1);
 	}
 
+	if (icr & IGC_ICR_TS)
+		igc_tsync_interrupt(adapter);
+
 	napi_schedule(&q_vector->napi);
 
 	return IRQ_HANDLED;