JCG Y2 is an AC1300M router

Hardware specs:
  SoC: MediaTek MT7621AT
  Flash: Winbond W25Q128JVSQ 16MiB
  RAM: Nanya NT5CB128M16 256MiB
  2.4GHz: MT7615D 2x2
  5GHz: MT7615D 2x2
  Ethernet: 1 x WAN and 4 x LAN
  LED: POWER, INTERNET, 2.4G, 5G
  USB: 1 x 3.0
  Button: Reset

Flash instructions:
  Upload factory.bin in stock firmware's upgrade page.
Signed-off-by: NAmadeusGhost <amadeus@jmu.edu.cn>