r8169: fix cable re-plugging issue

Bartek reported that after few cable unplug/replug cycles suddenly
replug isn't detected any longer. His system uses a RTL8106, I wasn't
able to reproduce the issue with RTL8168g. According to his bisect
the referenced commit caused the regression. As Realtek doesn't
release datasheets or errata it's hard to say what's the actual root
cause, but this change was reported to fix the issue.

Fixes: 38caff5a ("r8169: handle all interrupt events in the hard irq handler")
Reported-by: NBartosz Skrzypczak <barteks2x@gmail.com>
Suggested-by: NBartosz Skrzypczak <barteks2x@gmail.com>
Tested-by: NBartosz Skrzypczak <barteks2x@gmail.com>
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169.c

@@ -6542,7 +6542,7 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 		set_bit(RTL_FLAG_TASK_RESET_PENDING, tp->wk.flags);
 	}
 
-	if (status & RTL_EVENT_NAPI) {
+	if (status & (RTL_EVENT_NAPI | LinkChg)) {
 		rtl_irq_disable(tp);
 		napi_schedule_irqoff(&tp->napi);
 	}