ramips: add support for the VoCore2 Lite

ramips: add support for the VoCore2 Lite

The VoCore2 Lite uses the same PCB as the Vocore2.
This patch moves the common VoCore2 parts into dtsi.

Removed memory node in the device tree source file.
Memory is detected automatically.

http://vocore.io/
http://vonger.net/
http://vonger.cn/

Specifications:
- SoC: MediaTek MT7688AN
- RAM: 64MB DDR2 EtronTech EM68B16CWQH-25H
- Flash: 8MB NOR SPI Flash GigaDevice GD25Q64CWIG
- Wireless: Built into MT7688AN with onboard IPEX connector

Firmware installation:
- VoCore2-Lite ships with firmware forked from OpenWrt.
- Installation from the bootloader is recommended.
- If using luci/sysupgrade use the -n option (do not keep settings)
  original firmware uses a modified proprietary MediaTek wireless driver.
- The wireless is disabled by default in LEDE.
- If reverting to factory firmware using the bootloader is recommended.

Signed-off-by: L. D. Pinney <ldpinney@gmail.com>
Tested by: Noble Pepper <noblepepper@gmail.com>