usb: phy: phy-generic: add the implementation of .set_suspend

Add clock operation at .set_suspend if the PHY has
suspend requirement, it can be benefit of power saving for
phy and the whole system (parent clock may also be disabled).

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/phy/phy-generic.c

@@ -59,6 +59,15 @@ EXPORT_SYMBOL_GPL(usb_phy_generic_unregister);
 
 static int nop_set_suspend(struct usb_phy *x, int suspend)
 {
+	struct usb_phy_generic *nop = dev_get_drvdata(x->dev);
+
+	if (!IS_ERR(nop->clk)) {
+		if (suspend)
+			clk_disable_unprepare(nop->clk);
+		else
+			clk_prepare_enable(nop->clk);
+	}
+
 	return 0;
 }