wifi: mt76: mt7996: fix beamform mcu cmd configuration

The bf_num field represents how many bands can support beamform, so set
the value to 3, and bf_bitmap represents the bitmap of bf_num.

Fixes: 98686cd2 ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
Signed-off-by: Howard Hsu <howard-yh.hsu@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7996/mcu.c

@@ -3307,8 +3307,8 @@ int mt7996_mcu_set_txbf(struct mt7996_dev *dev, u8 action)
 
 		tlv = mt7996_mcu_add_uni_tlv(skb, action, sizeof(*req_mod_en));
 		req_mod_en = (struct bf_mod_en_ctrl *)tlv;
-		req_mod_en->bf_num = 2;
-		req_mod_en->bf_bitmap = GENMASK(0, 0);
+		req_mod_en->bf_num = 3;
+		req_mod_en->bf_bitmap = GENMASK(2, 0);
 		break;
 	}
 	default: