usbmode: add modeswitch rule for ZTE MF833U1

usbmode: add modeswitch rule for ZTE MF833U1

ZTE MF833U1 is a LTE dongle that expose a cdc_ether interface for data link
and WebUI for management. It handles all the "modem" functionalities
internally and does not expose any serial interface. Instead it acts like a
"router in a stick".

It initially enumerates as a USB mass-storage device and does not bind any
network driver, so no netdev is created until a modeswitch is performed.

The test is done on Cudy TR3000 256MB v1.0 running OpenWrt 24.10.5 with an
unit targeting Chinese market:

 - Hardware Version: MF883U1_V1.0.0
 - Software Version: BD_MF883U1V1.0.0B06
 - CMIT ID: 2019CP2106

There are report online that the device have different variants that have
different behavior across different firmware, HW revisions or SKUs.

Before the switch:

```
root@OpenWrt:~# lsusb -t
  /:  Bus 001.Port 001: Dev 001, Class=root_hub, Driver=xhci-mtk/1p, 480M
      |__ Port 001: Dev 003, If 0, Class=[unknown], Driver=[none], 480M

root@OpenWrt:~# lsusb Bus 001 Device 001: ID 1d6b:0002 Linux 6.6.119
xhci-hcd xHCI Host Controller Bus 001 Device 004: ID 19d2:1705
DEMO,Incorporated DEMO Mobile Boardband Bus 002 Device 001: ID 1d6b:0003
Linux 6.6.119 xhci-hcd xHCI Host Controller ```

After the switch:

```
root@OpenWrt:~# lsusb -t
  /:  Bus 001.Port 001: Dev 001, Class=root_hub, Driver=xhci-mtk/1p, 480M
      |__ Port 001: Dev 003, If 0, Class=[unknown], Driver=cdc_ether, 480M
      |__ Port 001: Dev 003, If 1, Class=[unknown], Driver=cdc_ether, 480M
      |__ Port 001: Dev 003, If 2, Class=[unknown], Driver=[none], 480M
  /:  Bus 002.Port 001: Dev 001, Class=root_hub, Driver=xhci-mtk/1p, 20000M/x2

root@OpenWrt:~# lsusb Bus 001 Device 001: ID 1d6b:0002 Linux 6.6.119
xhci-hcd xHCI Host Controller Bus 001 Device 003: ID 19d2:1706
DEMO,Incorporated DEMO Mobile Boardband Bus 002 Device 001: ID 1d6b:0003
Linux 6.6.119 xhci-hcd xHCI Host Controller ```

The following kernel debug log is presented:

``` cdc_ether 1-1:1.0 eth2: register 'cdc_ether' at usb-11200000.usb-1, ZTE
CDC Ethernet Device, 34:4b:50:00:00:00 ```

Signed-off-by: Zihao Diao <hi@ericdiao.com>
Link: https://github.com/openwrt/openwrt/pull/21867
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>