mt76: mt7915: allow beaconing on all chains

This improves rate reach performance on units with polarized antennas.
Signed-off-by: NRyder Lee <ryder.lee@mediatek.com>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/mac.c

@@ -1101,6 +1101,7 @@ mt7915_mac_write_txwi_80211(struct mt7915_dev *dev, __le32 *txwi,
 	if (ieee80211_is_beacon(fc)) {
 		txwi[3] &= ~cpu_to_le32(MT_TXD3_SW_POWER_MGMT);
 		txwi[3] |= cpu_to_le32(MT_TXD3_REM_TX_COUNT);
+		txwi[7] |= cpu_to_le32(FIELD_PREP(MT_TXD7_SPE_IDX, 0x18));
 	}
 
 	if (info->flags & IEEE80211_TX_CTL_INJECTED) {