wifi: mt76: mt7996: fix mt7996_mcu_all_sta_info_event struct packing

The internal struct and union inside mt7996_mcu_all_sta_info_event is
marked as being aligned, which conflicts with it being unaligned
within that structure:

drivers/net/wireless/mediatek/mt76/mt7996/mcu.h:165:2: error: field  within 'struct mt7996_mcu_all_sta_info_event' is less aligned than 'union mt7996_mcu_all_sta_info_event::(anonymous at ../drivers/net/wireless/mediatek/mt76/mt7996/mcu.h:165:2)' and is usually due to 'struct mt7996_mcu_all_sta_info_event' being packed, which can lead to unaligned accesses [-Werror,-Wunaligned-access]

Mark all three as being packed as well to ensure byte packing for
the entire thing.

Fixes: adde3eed ("wifi: mt76: mt7996: Add mcu commands for getting sta tx statistic")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -212,15 +212,15 @@ struct mt7996_mcu_all_sta_info_event {
 			u8 rsv[2];
 			__le32 tx_bytes[IEEE80211_NUM_ACS];
 			__le32 rx_bytes[IEEE80211_NUM_ACS];
-		} adm_stat[0];
+		} adm_stat[0] __packed;
 
 		struct {
 			__le16 wlan_idx;
 			u8 rsv[2];
 			__le32 tx_msdu_cnt;
 			__le32 rx_msdu_cnt;
-		} msdu_cnt[0];
-	};
+		} msdu_cnt[0] __packed;
+	} __packed;
 } __packed;
 
 struct mt7996_mcu_wed_rro_event {