rsi: fix spelling mistake "Uknown" -> "Unknown"

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

drivers/net/wireless/rsi/rsi_91x_mac80211.c

@@ -1103,7 +1103,7 @@ static int rsi_mac80211_ampdu_action(struct ieee80211_hw *hw,
 		break;
 
 	default:
-		rsi_dbg(ERR_ZONE, "%s: Uknown AMPDU action\n", __func__);
+		rsi_dbg(ERR_ZONE, "%s: Unknown AMPDU action\n", __func__);
 		break;
 	}