wifi: mt76: fix uninitialized pointer in mt7921_mac_fill_rx

Initialize msta pointer to NULL in mt7921_mac_fill_rx() in order to not
dereference a uninitialized pointer.

Fixes: 0880d40 ("mt76: connac: move mt76_connac2_reverse_frag0_hdr_trans in mt76-connac module")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7921/mac.c

@@ -235,7 +235,7 @@ mt7921_mac_fill_rx(struct mt7921_dev *dev, struct sk_buff *skb)
 	u32 rxd2 = le32_to_cpu(rxd[2]);
 	u32 rxd3 = le32_to_cpu(rxd[3]);
 	u32 rxd4 = le32_to_cpu(rxd[4]);
-	struct mt7921_sta *msta;
+	struct mt7921_sta *msta = NULL;
 	u16 seq_ctrl = 0;
 	__le16 fc = 0;
 	u8 mode = 0;