rsi: fix spelling mistake: "thead" -> "thread"

Trivial fix to spelling mistake in rsi_dbg debug message text
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/rsi/rsi_91x_core.c

@@ -485,7 +485,7 @@ void rsi_core_xmit(struct rsi_common *common, struct sk_buff *skb)
 	}
 
 	rsi_core_queue_pkt(common, skb);
-	rsi_dbg(DATA_TX_ZONE, "%s: ===> Scheduling TX thead <===\n", __func__);
+	rsi_dbg(DATA_TX_ZONE, "%s: ===> Scheduling TX thread <===\n", __func__);
 	rsi_set_event(&common->tx_thread.event);
 
 	return;