iwl4965: fix not correctly dealing with hotunplug

The interrupt handler returns IRQ_NONE if it detects that the device
is gone. That's incorrect because the device may have raised the interrupt.
Not acknowledging it may trigger the spurious interrupt detection and kill
drivers sharing the interrupt line.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl4965-base.c

@@ -5156,9 +5156,10 @@ static irqreturn_t iwl_isr(int irq, void *data)
 	}
 
 	if ((inta == 0xFFFFFFFF) || ((inta & 0xFFFFFFF0) == 0xa5a5a5a0)) {
-		/* Hardware disappeared */
+		/* Hardware disappeared. It might have already raised
+		 * an interrupt */
 		IWL_WARNING("HARDWARE GONE?? INTA == 0x%080x\n", inta);
-		goto none;
+		goto unplugged;
 	}
 
 	IWL_DEBUG_ISR("ISR inta 0x%08x, enabled 0x%08x, fh 0x%08x\n",
@@ -5166,8 +5167,9 @@ static irqreturn_t iwl_isr(int irq, void *data)
 
 	/* iwl_irq_tasklet() will service interrupts and re-enable them */
 	tasklet_schedule(&priv->irq_tasklet);
-	spin_unlock(&priv->lock);
 
+ unplugged:
+	spin_unlock(&priv->lock);
 	return IRQ_HANDLED;
 
  none: