rt2x00: fix use of mcs rates

In case of mcs rates txrate->idx contains the mcs index to be used for
transmission. Previously the mcs values dedicated for legacy rates where
used for mcs transmissions which resulted in the use of mcs 0 in a number
of cases (e.g. for all mcs rates >= 15 as rt2x00 does not register legacy
rates with indexes >= 15).
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>

drivers/net/wireless/rt2x00/rt2x00ht.c

@@ -48,9 +48,18 @@ void rt2x00ht_create_tx_descriptor(struct queue_entry *entry,
 	txdesc->stbc =
 	    (tx_info->flags & IEEE80211_TX_CTL_STBC) >> IEEE80211_TX_CTL_STBC_SHIFT;
 
+	/*
+	 * If IEEE80211_TX_RC_MCS is set txrate->idx just contains the
+	 * mcs rate to be used
+	 */
+	if (txrate->flags & IEEE80211_TX_RC_MCS) {
+		txdesc->mcs = txrate->idx;
+	} else {
 		txdesc->mcs = rt2x00_get_rate_mcs(hwrate->mcs);
 		if (txrate->flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE)
 			txdesc->mcs |= 0x08;
+	}
+
 
 	/*
 	 * Convert flags