MIPS: OCTEON: Remove unneeded OCTEON_IRQ_* defines.

The follow-on patch to add irq_domain support will be the supported
method for using these irq lines, so get these defines out of the way
in preperation for that.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc:  linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3930/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>