mt76: mt7915: fix info leak in mt7915_mcu_set_pre_cal()

Zero out all the unused members of "req" so that we don't disclose
stack information.

Fixes: 495184ac ("mt76: mt7915: add support for applying pre-calibration data")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NFelix Fietkau <nbd@nbd.name>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>

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

@@ -3481,7 +3481,7 @@ static int mt7915_mcu_set_pre_cal(struct mt7915_dev *dev, u8 idx,
 		u8 idx;
 		u8 rsv[4];
 		__le32 len;
-	} req;
+	} req = {};
 	struct sk_buff *skb;
 
 	skb = mt76_mcu_msg_alloc(&dev->mt76, NULL, sizeof(req) + len);