MIPS: Octeon: Run IPI code with interrupts disabled.

In mm/slab.c the function do_ccupdate_local requires that interrupts be
disabled.  If they are not, we panic with CONFIG_DEBUG_SLAB.

So we disable interrupts while processing IPIs.  Also these are not shared
irqs, so get rid of the IRQF_SHARED flag.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>