r8169: Disable clk during suspend / resume

Disable the clk during suspend to save power. Note that tp->clk may be
NULL, the clk core functions handle this without problems.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169.c

@@ -6869,8 +6869,10 @@ static int rtl8169_suspend(struct device *device)
 {
 	struct pci_dev *pdev = to_pci_dev(device);
 	struct net_device *dev = pci_get_drvdata(pdev);
+	struct rtl8169_private *tp = netdev_priv(dev);
 
 	rtl8169_net_suspend(dev);
+	clk_disable_unprepare(tp->clk);
 
 	return 0;
 }
@@ -6898,6 +6900,9 @@ static int rtl8169_resume(struct device *device)
 {
 	struct pci_dev *pdev = to_pci_dev(device);
 	struct net_device *dev = pci_get_drvdata(pdev);
+	struct rtl8169_private *tp = netdev_priv(dev);
+
+	clk_prepare_enable(tp->clk);
 
 	if (netif_running(dev))
 		__rtl8169_resume(dev);