[New Device] ramips: add support for Dragonglass DGR7 (16M flash)

Dragonglass DGR7 (16M flash variant) — Request for Review

This adds the 16M flash variant of the Dragonglass DGR7, using the full 16 MB XM25QH128A SPI NOR flash with approximately 15.4 MB of usable firmware space.

Differs from the 8M variant

  • Firmware partition: 0xa0000-0x1000000 (15744k vs 7552k)
  • Compatible: dragonglass,dgr7-16m

Hardware same as 8M variant

  • SoC: MediaTek MT7621A
  • RAM: 128 MB DDR2
  • WiFi: MT7603E + MT7612E (AC1200)
  • Ethernet: 5x 1GbE DSA (port 0-3 LAN, port 4 WAN)

Status

Would appreciate any review. Thanks!

-- Ivan Lee