ramips: add support for the Hak5 WiFi Pineapple Mark 7

ramips: add support for the Hak5 WiFi Pineapple Mark 7

This patch adds support for the WiFi Pineapple Mark 7, a wireless
penetration testing tool.

Specifications:
    * SoC: MediaTek MT7628 (580MHz)
    * RAM: 256MiB (DDR2)
    * Storage 1: 32MiB NOR (SPI)
    * Storage 2: 2GB eMMC
    * Wireless 1: 802.11b/g/n 2.4GHz (Built In)
    * Wireless 2: 802.11b/g/n 2.4GHz (MT7601)
    * Wireless 3: 802.11b/g/n 2.4GHz (MT7601)
    * USB: 1x USB Type-A 2.0 Host Port
    * Ethernet: 1x USB Type-C AX88772C Ethernet
    * UART: 57600 8N1 on PCB
    * Inputs: 1x Reset Button
    * Outputs: 1x RGB LED
    * FCCID: 2AA52MK7

Flash Instructions:
    Original firmware is based on OpenWRT.
    Use sysupgrade via SSH to flash.

Signed-off-by: Marc Egerton <foxtrot@realloc.me>
[pepe2k@gmail.com: set only required/used gpio groups to gpio function]
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>