ramips: add support for OpenFi 5Pro Travel Router

ramips: add support for OpenFi 5Pro Travel Router

OpenFi 5Pro is a DualBand Travel Router, based on MT7621A.

Specification:
- Type             : Travel Wi-Fi Router(built-in Type-C Power Cable)
- Size             : 63 x 93 x 24mm
- Power            : Internal Type-C Cable PD/DC 5V@2A
- SoC              : MediaTek MT7621A
- RAM              : DDR3 512 MB
- Flash            : SPI-NOR 64MB (W25Q512)
- WLAN             : 2.4/5GHz 2T2R (MediaTek MT7603e/MT7613)
- Ethernet         : 2x 10/100/1000Mbps
- USB              : 1 x USB 2.0
- SDHCI            : 1 x TF Slot (Max 512GB)
- LEDs             : 3 x LEDs  (GPIO#16 gpio#17 gpio#14)
- Button           : 1 x Reset (GPIO#18),  1 x WPS (GPIO#13)
- UART             : 1 x UART for Debug, 115200 8N1 (Pinout: GND TX RX 3.3V)
- UART 2           : 1xUART2  (Pinout: GND TX2 RX2 3.3V )

How to upgrade image in uboot

1. press reset button when boot for 5sec.
2. access 192.168.21.1 in web ui.
3. select image and upload

Signed-off-by: Sven Huang <1036456939@qq.com>