Add DTS for EdgeRouter Lite that is usable as is without any "pruning"
with APPENDED_DTB.

Compared to builtin generic DTB, we can avoid errors and delays from
probing non-existent I2C devices.
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>