staging: vt6655: device_intr check for vif on while loop

vif should never be or go null while in loop.

Fixes race condition where interrupts are late and when
interface is not present.
Signed-off-by: NMalcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6655/device_main.c

@@ -1090,7 +1090,7 @@ static  irqreturn_t  device_intr(int irq,  void *dev_instance)
 	 * update ISR counter
 	 */
 	STAvUpdate802_11Counter(&pDevice->s802_11Counter, &pDevice->scStatistic, dwMIBCounter);
-	while (pDevice->dwIsr != 0) {
+	while (pDevice->dwIsr && pDevice->vif) {
 		STAvUpdateIsrStatCounter(&pDevice->scStatistic, pDevice->dwIsr);
 		MACvWriteISR(pDevice->PortOffset, pDevice->dwIsr);
 
@@ -1102,8 +1102,7 @@ static  irqreturn_t  device_intr(int irq,  void *dev_instance)
 		}
 
 		if (pDevice->dwIsr & ISR_TBTT) {
-			if (pDevice->vif &&
-			    pDevice->op_mode != NL80211_IFTYPE_ADHOC)
+			if (pDevice->op_mode != NL80211_IFTYPE_ADHOC)
 				vnt_check_bb_vga(pDevice);
 
 			pDevice->bBeaconSent = false;
@@ -1143,19 +1142,15 @@ static  irqreturn_t  device_intr(int irq,  void *dev_instance)
 			max_count += device_tx_srv(pDevice, TYPE_AC0DMA);
 
 		if (pDevice->dwIsr & ISR_SOFTTIMER1) {
-			if (pDevice->vif) {
-				if (pDevice->vif->bss_conf.enable_beacon)
-					vnt_beacon_make(pDevice, pDevice->vif);
-			}
+			if (pDevice->vif->bss_conf.enable_beacon)
+				vnt_beacon_make(pDevice, pDevice->vif);
 		}
 
 		/* If both buffers available wake the queue */
-		if (pDevice->vif) {
-			if (AVAIL_TD(pDevice, TYPE_TXDMA0) &&
-			    AVAIL_TD(pDevice, TYPE_AC0DMA) &&
-			    ieee80211_queue_stopped(pDevice->hw, 0))
-				ieee80211_wake_queues(pDevice->hw);
-		}
+		if (AVAIL_TD(pDevice, TYPE_TXDMA0) &&
+		    AVAIL_TD(pDevice, TYPE_AC0DMA) &&
+		    ieee80211_queue_stopped(pDevice->hw, 0))
+			ieee80211_wake_queues(pDevice->hw);
 
 		MACvReadISR(pDevice->PortOffset, &pDevice->dwIsr);