ath79: Add GL.iNet AR-300M-Lite

ath79: Add GL.iNet AR-300M-Lite

AR300M-Lite is single-Ethernet variant of the AR300M series
Its eth0 would otherwise be assigned to the WAN interface
making it unreachable firstboot or failsafe.

Installation instructions from OEM (OpenWrt variant):
* Install sysupgrade.bin using OEM's "Advanced" GUI (LuCI),
   * Do not preserve settings
   * Access rebooted device via Ethernet at OpenWrt default address

Add previously missing LED defaults for all three variants;
-nand, -nor, -lite to the definitions in 01_leds

Non-lite variants thanks to Andreas Ziegler
https://patchwork.ozlabs.org/patch/1049396/

Runtime-tested:  GL.iNet AR300M-Lite

Signed-off-by: Jeff Kletsky <git-commits@allycomm.com>