ramips: add support for TOZED ZLT S12 PRO

The TOZED ZLT S12 PRO is an AC1200 router featuring 4 Ethernet ports with a
TOZED TL70-C cellular modem which supports the NCM mode.

The stock firmware does SIM locking on the modem by stopping dialing when a
different PLMN is detected. This is not the case on OpenWrt.

Specifications:
- CPU: MediaTek MT7621AT
- RAM: 256MB DDR3
- NOR Flash: MX25L12833FM2I 16MB SPI Flash
- Wi-Fi 2.4Ghz: MT7603E
- Wi-Fi 5Ghz: MT7612E
- Switch: MT7530 4x 1Gbit Ports
- WWAN: Unisoc SL8563 based TOZED TL70-C LTE CAT6 cellular modem
- USB: 1x optional USB2.0 external port
- Switches/Buttons: WPS, Reset, Power Switch
- LEDs: Power, Wi-Fi, Data, Signal 1-5, Phone

Installation and TFTP Recovery:
- Connect to serial console.
- Boot initramfs image by choosing option 1 when U-Boot prompts.
- Install sysupgrade image via OpenWrt.

Serial Pins:
Located at the bottom right when looking from the front, right under the
Reset/WPS buttons. The pinout from the left is:
- RX
- GND
- TX
Baudrate is 115200.

When connecting from a powered off state, disconnect RX as it blocks the
boot process.

Link: http://www.sztozed.com/en/contents/58/84.html
Co-developed-by: Andre Cruz <me@1conan.com>
Signed-off-by: Andre Cruz <me@1conan.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>

target/linux/ramips/mt7621/base-files/etc/board.d/02_network

@@ -108,6 +108,10 @@ ramips_setup_interfaces()
 	mikrotik,routerboard-760igs)
 		ucidef_set_interfaces_lan_wan "lan2 lan3 lan4 lan5" "wan sfp"
 		;;
+	tozed,zlt-s12-pro)
+		ucidef_set_interface "wwan" device "/dev/ttyUSB0" protocol "ncm"
+		uci add_list firewall.@zone[1].network='wwan'
+		;;
 	tplink,deco-m4r-v4)
 		ucidef_set_interfaces_lan_wan "eth1" "eth0"
 		;;

target/linux/ramips/mt7621/base-files/etc/board.d/03_gpio_switches

@@ -12,6 +12,9 @@ mikrotik,routerboard-760igs)
 telco-electronics,x1)
 	ucidef_add_gpio_switch "modem_reset" "Modem Reset" "496"
 	;;
+tozed,zlt-s12-pro)
+	ucidef_add_gpio_switch "lt72_power" "Power LTE modem" "lt72_power" "1"
+	;;
 tplink,eap235-wall-v1|\
 tplink,eap615-wall-v1)
 	ucidef_add_gpio_switch "poe_passthrough" "PoE Passthrough" "poe-passthrough"