ipi is used to communicate between cpus, this patch modified
loongarch ipi device as percpu device, so that there are
2 MemoryRegions with ipi device, rather than 2*cpus
MemoryRegions, which may be large than QDEV_MAX_MMIO if
more cpus are added on loongarch virt machine.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20230512100421.1867848-2-gaosong@loongson.cn>