MIPS: Octeon: Remove use of OCTEON_IRQ_RST.

This symbol will be removed, so don't use it as part of the definition of
OCTEON_IRQ_LAST.

Set OCTEON_IRQ_LAST to 127 so there is space for all the automatically
allocated (via irq_domain) irqs.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3946/


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