rt2800: make rx ampdu_factor depend on number of rx chains

Initalize max ampdu_factor supported by us based on rx chains, vendor
driver do the same.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2800lib.c

@@ -7593,7 +7593,7 @@ static int rt2800_probe_hw_mode(struct rt2x00_dev *rt2x00dev)
 
 	spec->ht.cap |= rx_chains << IEEE80211_HT_CAP_RX_STBC_SHIFT;
 
-	spec->ht.ampdu_factor = 3;
+	spec->ht.ampdu_factor = (rx_chains > 1) ? 3 : 2;
 	spec->ht.ampdu_density = 4;
 	spec->ht.mcs.tx_params = IEEE80211_HT_MCS_TX_DEFINED;
 	if (tx_chains != rx_chains) {