libertas: submit RSSI command on tx timeout, to check whether module is dead

We don't necessarily want to reset the device on a TX timeout. But more
often than not, the real cause is that the firmware has crapped itself,
not just that the network is busy. So submit any harmless command, and
if _that_ times out, then the error handling code will reset the module,
as appropriate.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/main.c

@@ -476,6 +476,13 @@ static void lbs_tx_timeout(struct net_device *dev)
 	   to kick it somehow? */
 	lbs_host_to_card_done(priv);
 
+	/* More often than not, this actually happens because the
+	   firmware has crapped itself -- rather than just a very
+	   busy medium. So send a harmless command, and if/when
+	   _that_ times out, we'll kick it in the head. */
+	lbs_prepare_and_send_command(priv, CMD_802_11_RSSI, 0,
+				     0, 0, NULL);
+
 	lbs_deb_leave(LBS_DEB_TX);
 }