mt76: fix a leaked reference by adding a missing of_node_put

The call to of_find_node_by_phandle returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

Detected by coccinelle with the following warnings:
./drivers/net/wireless/mediatek/mt76/eeprom.c:58:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 48, but without a corresponding object release within this function.
./drivers/net/wireless/mediatek/mt76/eeprom.c:61:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 48, but without a corresponding object release within this function.
./drivers/net/wireless/mediatek/mt76/eeprom.c:67:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 48, but without a corresponding object release within this function.
./drivers/net/wireless/mediatek/mt76/eeprom.c:70:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 48, but without a corresponding object release within this function.
./drivers/net/wireless/mediatek/mt76/eeprom.c:72:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 48, but without a corresponding object release within this function.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Felix Fietkau <nbd@nbd.name>
Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mediatek@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mediatek/mt76/eeprom.c

@@ -54,22 +54,30 @@ mt76_get_of_eeprom(struct mt76_dev *dev, int len)
 		part = np->name;
 
 	mtd = get_mtd_device_nm(part);
-	if (IS_ERR(mtd))
-		return PTR_ERR(mtd);
+	if (IS_ERR(mtd)) {
+		ret =  PTR_ERR(mtd);
+		goto out_put_node;
+	}
 
-	if (size <= sizeof(*list))
-		return -EINVAL;
+	if (size <= sizeof(*list)) {
+		ret = -EINVAL;
+		goto out_put_node;
+	}
 
 	offset = be32_to_cpup(list);
 	ret = mtd_read(mtd, offset, len, &retlen, dev->eeprom.data);
 	put_mtd_device(mtd);
 	if (ret)
-		return ret;
+		goto out_put_node;
 
-	if (retlen < len)
-		return -EINVAL;
+	if (retlen < len) {
+		ret = -EINVAL;
+		goto out_put_node;
+	}
 
-	return 0;
+out_put_node:
+	of_node_put(np);
+	return ret;
 #else
 	return -ENOENT;
 #endif