MIPS: lantiq: copy the commandline from the devicetree

This is a regression caused by:
commit afb46f79


Author: Rob Herring <robh@kernel.org>
Date:   Wed Apr 2 19:07:24 2014 -0500
mips: ralink: convert to use unflatten_and_copy_device_tree

Make the of init code reuse the cmdline defined inside the dts.

Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/8048/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>