MIPS: CMP: Extend the GIC IPI interrupts beyond 32

This patch extends the GIC interrupt handling beyond the current 32 bit
range as well as extending the number of interrupts based on the number
of CPUs.

Signed-off-by: Tim Anderson <tanderson@mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>