Octeon doesn't use IRQ_CPU, so don't select it.

IRQ_CPU_OCTEON is a completely unused symbol, remove it completely.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2086/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>