ramips: fix support for Cudy r700

ramips: fix support for Cudy r700

This PR fixes support for Cudy r700.

Original PR: https://github.com/openwrt/openwrt/pull/18532
Fixed:

- WAN port functionality;
- RESET button;
- Status LED;
- LAN port names consistent with the chassis;
- Merged partitions "debug", "backup" & "firmware"  to one partition "firmware" ("debug" & "backup" contained unimportant data);
- Removed redundant DTS elements.

Installation:

To install OpenWRT, you need the intermediate firmware from Cudy. (U-boot is locked). After installing the intermediate firmware, you can install OpenWRT via sysupgrade.

Recovery:

TFTP available.
1. Place the recovery.bin in the serving directory of your TFTP server.
2. Set your IP to 192.168.1.88/24.
3. Press the “Reset” button of Cudy router and hold it. Before the Cudy router is powered on and before TFTP start to download the firmware, don't release the “Reset” button.
4. Power on the Cudy router.
5. You can release the reset button only when TFTP starts downloading firmware.
6. When the SYSTEM LED turns solid green, the upgrade is complete.

Fixes: 75403dd1d05b ("ramips: add support for Cudy R700")
Link: https://github.com/openwrt/openwrt/pull/20756
(cherry picked from commit 35a86267e90312f24fd11553cd5a5db0736b79ca)
Signed-off-by: Marcin Leksmark <lexmark3200@wp.pl>
Link: https://github.com/openwrt/openwrt/pull/21068
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>