MIPS: Octeon: Remove special case for simulator command line.

There is no reason to have the kernel to append commands when running
under the simulator, the simulator is perfectly capable of supplying
the necessary command line arguments.  Furthermore, if the simulator
needs something different than what is hard coded in the kernel, it
cannot get it if the kernel overrides it.

Fix/Simplify the whole thing by removing this bit.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8152/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>