ramips: add support for ipTIME T5004
ipTIME T5004 is a 5-port Gigabit Ethernet router, based on MediaTek MT7621A.
Specifications:
* SoC: MT7621AT
* RAM: 128 MiB
* Flash: NAND 128 MiB
* Ethernet: 5x 1GbE
* Switch: SoC built-in
* UART: J4 (57600 baud)
* Pinout: [3V3] (TXD) (RXD) (GND)
Installation via web interface:
1. Flash **initramfs** image through the stock web interface.
2. Boot into OpenWrt and perform sysupgrade with sysupgrade image.
Revert to stock firmware via recovery mode:
1. Press reset button, power up the device, wait >15s for CPU LED
to stop blinking.
2. Upload stock image to TFTP server at 192.168.0.1.
Signed-off-by: Sungbo Eo <mans0n@gorani.run>