staging: vt6655: Correct listen interval TBTT wake up

PSbIsNextTBTTWakeUp is called at beacon intervals.

The should listen to next beacon on count down of wake_up_count == 1.

This restores this back to vendors code but modified for mac80211.
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6655/device.h

@@ -403,6 +403,7 @@ struct vnt_private {
 	unsigned char abyEEPROM[EEP_MAX_CONTEXT_SIZE]; /* unsigned long alignment */
 
 	unsigned short wBeaconInterval;
+	u16 wake_up_count;
 
 	struct work_struct interrupt_work;
 

drivers/staging/vt6655/power.c

@@ -157,10 +157,18 @@ PSbIsNextTBTTWakeUp(
 	struct ieee80211_conf *conf = &hw->conf;
 	bool bWakeUp = false;
 
-	if (conf->listen_interval == 1) {
-		/* Turn on wake up to listen next beacon */
-		MACvRegBitsOn(pDevice->PortOffset, MAC_REG_PSCTL, PSCTL_LNBCN);
-		bWakeUp = true;
+	if (conf->listen_interval > 1) {
+		if (!pDevice->wake_up_count)
+			pDevice->wake_up_count = conf->listen_interval;
+
+		--pDevice->wake_up_count;
+
+		if (pDevice->wake_up_count == 1) {
+			/* Turn on wake up to listen next beacon */
+			MACvRegBitsOn(pDevice->PortOffset,
+				      MAC_REG_PSCTL, PSCTL_LNBCN);
+			bWakeUp = true;
+		}
 	}
 
 	return bWakeUp;