r8169: don't try to disable interrupts if NAPI is scheduled already

There's no benefit in trying to disable interrupts if NAPI is
scheduled already. This allows us to save a PCI write in this case.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/78c7f2fb-9772-1015-8c1d-632cbdff253f@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/realtek/r8169_main.c

@@ -4549,8 +4549,10 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 		rtl_schedule_task(tp, RTL_FLAG_TASK_RESET_PENDING);
 	}
 
-	rtl_irq_disable(tp);
-	napi_schedule(&tp->napi);
+	if (napi_schedule_prep(&tp->napi)) {
+		rtl_irq_disable(tp);
+		__napi_schedule(&tp->napi);
+	}
 out:
 	rtl_ack_events(tp, status);